A battery is considered connected when a) V > BOARD_ADC_OPEN_CIRCUIT_V
   and if BOARD_ADC_OPEN_CIRCUIT_V > BOARD_VALID_UV connected
   is further qualifed by the Valid signal.

   Due to higher bias, V open circuit on the ADC is high with a 1M
   termination. This override the default connected threshold on
   V5 HW. Revist once lowe termination is chosen.

   Based on the R values on the LTC4411 the px4fmu-v4pro has a
   UV of 4.01 Volts.

   BOARD_ADC_OPEN_CIRCUIT_V is the voltage present on an ADC due
   to the bias current on the terminition resistor.

   BOARD_VALID_UV is the under voltage min set by resistors on a
   board's Power selector.

   A battery is considered connected when the Voltage measures is
   greater than BOARD_ADC_OPEN_CIRCUIT_V.

   In the case where BOARD_ADC_OPEN_CIRCUIT_V is greater then
   BOARD_VALID_UV we can use the HW to qualify connected.

   Connected is assumed when the battery voltages is greater than
   a predefined level.

   The data sheet for the F4, F7 indicate a maximum of 36 Mhz
   in the 2.4-3.3 volt Soc operating range. This change sets
   the clock based on the STM32_PCLK2_FREQUENCY.

   Upstream change on F7 CONFIG_STM32F7_FLASH_PREFETCH and
   CONFIG_ARMV7M_ITCM are now contorled by
   CONFIG_STM32F7_FLASH_ART_ACCELERATOR

* NuttX cmake

* px4_macros:Pass the stringified predicate as second arg to static assert

   CC_ASSERT mapes to the c++ static_assert or provides the same
   funtionality for c via the other macros. The c++ static assert
   takes 2 argumants the prdicate and a message. This fixes the
   lacking second argument.

* Updated nuttx and apps submodule to upstream nuttx 7.21+==master

   This is the latest uptake of upstream nuttx and apps.

* ROMFS generate with xxd instead of objcopy

* delete nuttx-patches

* NuttX update submodules to latest px4_nuttx-master

* fix nuttx apps and board dependency

* docker_run update to latest container 2017-08-29

* cmake ROMFS portable sed usage

* NuttX update submodules to latest px4_nuttx-master

    was:CONFIG_SCHED_HPWORKPRIORITY=192
    is:CONFIG_SCHED_HPWORKPRIORITY=249

   Updated to match master
   This is needed when logger is logging to file and ulog streaming gets
   activated

    was:CONFIG_SCHED_HPWORKPRIORITY=192
    is:CONFIG_SCHED_HPWORKPRIORITY=249

   Airspeed changes
   add FastRTPS