what could have gone wrong before? A scheduling switch during the printload
could have led to a task exit, rendering the tcb invalid. After switching
back, printload would access invalid memory.

This keeps the sched_lock() section as small as possible, just grabbing the
tcb variables we need.

Also when formatting malvink mission items from internal mission items,
the INT flag should be obeyed.

The relative altitude flag was not set correclty when waypoints are sent
using the INT protocol.

       1) Revert the inherited dma bug from the stm32
       see https://bitbucket.org/nuttx/nuttx/commits/df9ae3c13fc2fff2c21ebdb098c520b11f43280d
       for details.

       2) Most all CR1-CR3 settings can not be configured while UE
          is true. Threfore we make all operation atomic and disable
          UE and restore it's originalstate on exit.

       N.B. This backport omits all upstream breaking changes.

   FMUv4 PRO HW does not have a controlable V3.3 on the connector
   it therefore can not support the SPEKTUM binding.
   This PR removes the Power switch controls or binding control
   interfaces from the board config

   Removed the legacy FMUv4 define that was activating a nonexistent
   pull up and on some HW driving the PPM_IN aka RC_IN aka SPEKTRUM_RX
   to VDD.

   Also detailed the connections of this pins for the board.

   The simplest connection is RC_IN to a timer capture pin
   and a UART.
   In this case the UART_RX pin and just be left as is.
   While the pin can be configured as the PPM_IN (Timer capture)
   or as SPEKTRUM_RX_AS_GPIO_OUTPUT to use it as and GPIO to
   facilitate binding.

  Renamed the macros and defines to be more explicit as to what
  Is being done and the sense of the parameters

   Removed the legacy FMUv4 define that was activating a nonexistent
   pull up and on some HW driving the PPM_IN aka RC_IN aka SPEKTRUM_RX
   to VDD.

   Also detailed the connections of this pins for the board.

   The simplest connection is RC_IN to a timer capture pin
   and a UART.
   In this case the UART_RX pin and just be left as is.
   While the pin can be configured as the PPM_IN (Timer capture)
   or as SPEKTRUM_RX_AS_GPIO_OUTPUT to use it as and GPIO to
   facilitate bindin

  Renamed the macros and defines to be more explicit as to what
  Is being done and the sense of the parameters

   Removed the legacy FMUv4 define that was activating a nonexistent
   pull up and on some HW driving the PPM_IN aka RC_IN aka SPEKTRUM_RX
   to VDD.

   Also detailed the connections of this pins for the board.

   The simplest connection is RC_IN to a timer capture pin
   and a UART.
   In this case the UART_RX pin and just be left as is.
   While the pin can be configured as the PPM_IN (Timer capture)
   or as SPEKTRUM_RX_AS_GPIO_OUTPUT to use it as and GPIO to

  Renamed the macros and defines to be more explicit as to what
  Is being done and the sense of the parameters

   Removed the legacy FMUv4 define that was activating a nonexistent
   pull up and on some HW driving the PPM_IN aka RC_IN aka SPEKTRUM_RX
   to VDD.

   Also detailed the connections of this pins for the board.

   The simplest connection is RC_IN to a timer capture pin
   and a UART.
   In this case the UART_RX pin and just be left as is.
   While the pin can be configured as the PPM_IN (Timer capture)
   or as SPEKTRUM_RX_AS_GPIO_OUTPUT to use it as and GPIO to
   facilitate binding.

  Renamed the macros and defines to be more explicit as to what
  Is being done and the sense of the parameters

   Removed the legacy FMUv4 define that was activating a nonexistent
   pull up and on some HW driving the PPM_IN aka RC_IN aka SPEKTRUM_RX
   to VDD.

   Also detailed the connections of this pins for the board.

   The simplest connection is RC_IN to a timer capture pin
   and a UART.
   In this case the UART_RX pin and just be left as is.
   While the pin can be configured as the PPM_IN (Timer capture)
   or as SPEKTRUM_R
   facilitate binding.

  Renamed the macros and defines to be more explicit as to what
  Is being done and the sense of the parameters

   Removed the legacy FMUv4 define that was activating a nonexistent
   pull up and on some HW driving the PPM_IN aka RC_IN aka SPEKTRUM_RX
   to VDD.

   Also detailed the connections of this pins for the board.

   The simplest connection is RC_IN to a timer capture pin
   and a UART.
   In this case the UART_RX pin and just be left as is.
   While the pin can be configured as the PPM_IN (Timer capture)
   or as SPEKTRUM_RX_AS_GPIO_OUTPUT to use it as and GPIO to
   facilitate binding.

  Renamed the macros and defines to be more explicit as to what
  Is being done and the sense of the parameters

   Removed the legacy FMUv4 define that was activating a nonexistent
   pull up and on some HW driving the PPM_IN aka RC_IN aka SPEKTRUM_RX
   to VDD.

   Also detailed the connections of this pins for the board.

   The simplest connection is RC_IN to a timer capture pin
   and a UART.
   In this case the UART_RX pin and just be left as is.
   While the pin can be configured as the PPM_IN (Timer capture)
   or as SPEKTRUM_RX_AS_GPIO_OUTPUT to use it as and GPIO to
   facilitate binding.

  Renamed the macros and defines to be more explicit as to what
  Is being done and the sense of the parameters

   Removed the legacy FMUv4 define that was activating a nonexistent
   pull up and on some HW driving the PPM_IN aka RC_IN aka SPEKTRUM_RX
   to VDD.

   Also detailed the connections of this pins for the board.

   The simplest connection is RC_IN to a timer capture pin
   and a UART.
   In this case the UART_RX pin and just be left as is.
   While the pin can be configured as the PPM_IN (Timer capture)
   or as SPEKTRUM_RX_AS_GPIO_OUTPUT to use it as and GPIO to
   facilitate binding.

  Renamed the macros and defines to be more explicit as to what
  Is being done and the sense of the parameters

   Use the abstaction SPEKTRUM_POWER to enable the interface not
   the define for the GPIO pin.

   Use the clearer macro definitions

   Removed the legacy FMUv4 define that was activating a nonexistent
   pull up and on some HW driving the PPM_IN aka RC_IN aka SPEKTRUM_RX
   to VDD.

   Use the abstaction SPEKTRUM_POWER to enable the interface not
   the define for the GPIO pin.

   Removed the legacy FMUv4 define that was activating a nonexistent
   pull up and on some HW driving the PPM_IN aka RC_IN aka SPEKTRUM_RX
   to VDD.

   Also detailed the connections of this pins for the board.

   The simplest connection is RC_IN to a timer capture pin
   and a UART.
   In this case the UART_RX pin and just be left as is.
   While the pin can be configured as the PPM_IN (Timer capture)
   or as SPEKTRUM_RX_AS_GPIO_OUTPUT to use it as and GPIO to
   facilitate binding.

  Renamed the macros and defines to be more explicit as to what
  Is being done and the sense of the parameters

This range amkes much more sense for MAV applications.
It reduces vibration vulnerability caused by measurement range clipping.

Just to make sure that it will never be used on NuttX. This is not an
architectural limitation, just a memory optimization, since we call
clearenv() on NuttX.

This is duplicated in src/include/visibility and is directly included via
compiler flag '-include'

This is already added in px4_base.cmake and PX4_INCLUDE_DIR is not set
either.

To reduce dropouts, and because we have enough RAM :)

Frees up around 6kB of RAM on Pixracer & Pixhawk.

   Returned the fmu mixer code to where it updated the HW once
   it has a mixer. But  only signals a up_pwm_update() for
   onshots on actual control update.

   Before this change the hw outpuse were not updated.

* cmake: Fixes problem caused when the generated parameters.xml differs for the ARM and DSP builds.

* fix px4_getopt.h: add accidentally removed file

   A recent change in in the fmu stops the instance when a
   xxxx_reset command is used issued if the fmu was not
   already running.

   That change left publications published and then on the
   next creation created a new publications was created.

   This change calls orb_unadvertise to mark the publication
   as un published so that on the next instantiations of the
   fmu it resumes publishing on the same publication.