* mavlink receiver: added handling of battery status

handle incoming battery status messages in order to support external
battery monitoring

Signed-off-by: Roman <bapstr@ethz.ch>

* sensor params: added parameter for battery monitoring source

Signed-off-by: Roman <bapstr@ethz.ch>

* sensors: only publish battery status if we don't have external battery
monitoring activated

Signed-off-by: Roman <bapstr@ethz.ch>

* Update default parameters for TBS Caipirinha

* reverse channel 0 doesn't exist

fixed logic such that parameters are saved when vehicle just landed.
only save parameters once when state changed from in_air to landed.

Signed-off-by: tumbili &lt;roman@px4.io&gt; and bkueng <beat-kueng@gmx.net>

Signed-off-by: tumbili &lt;roman@px4.io&gt; and bkueng <beat-kueng@gmx.net>

fixes regression from 85245471

The flow control state is improperly reflected as enabled if the arch/HAL rejects an IOCTL to turn it on. Mavlink::enable_flow_control updates _flow_control_enabled only if the IOCTL call does not fail.

Signed-off-by: Roman <bapstr@ethz.ch>

Signed-off-by: Roman <bapstr@ethz.ch>

Signed-off-by: tumbili <roman@px4.io>

Signed-off-by: Roman <bapstr@ethz.ch>

Signed-off-by: Roman <bapstr@ethz.ch>

control state airspeed

this will enable small planes flying without an
airspeed sensor

* the OSX builds were spending the majority of the time just updating homebrew and installing a couple packages

* move gcc 4.9 build to circleci

* travis-ci update to xcode 7.3

* travis-ci limit git fetching for OSX

* Makefile split firmware targets for CI

* OSX ccache

- priority field uses only the lower 8 bits, so we can merge with the
  update_reported flag
- orb_set_interval is not used often, so make the necessary data an
  optional pointer and alloc only when needed.

Memory savings:
- pixracer (w. ekf2): 7.3kB
- pixhawk: 5.3kB

This brings some makefile and script fixes, as well as an updated dspal.

in altitude control mode for fixed wings the roll setpoint was not
logged because the position controller publishes the attitude setpoint
but the desired roll setpoint is calculated in the attitude control
module. Now the position controller calculates the roll setpoint as well
for the sake of logging.

Signed-off-by: tumbili <roman@px4.io>

-limited to 16 chars

Unfortunately, lot's of whitespace changes, required to satisfy unspecified code style format errors.