HAL_PX4: include visibility.h

needed for new nuttx structure
HAL_PX4: moved rc.APM to new ROMFS directory
PX4: added base ROMFS files from upstream
PX4: added in remaining example mixers
build: added support for the new PX4 build system
build: fixed build_binaries.sh for new PX4 build
PX4: auto-build the archives if needed
build: added px4-archives target
PX4: changed EXTRAFLAGS to EXTRADEFINES for PX4
PX4: need led driver in build for latest upstream changes
PX4: fixed px4io build in build_binaries.sh
build: fixed build_all_px4.sh for new PX4 build
Copter: only run nav controllers when auto-armed

This stops run-up in target position and nav controller I terms ahead of
throttle being raised
Copter: remove redundant init of controllers when auto is started

individual do_* commands are responsible for setting roll-pitch, yaw and
throttle modes.  Removing this redundant setting of the controllers
removes the short period (10th second max) where loiter and waypoint
controller's desired roll and pitch were used even before the
controllers have been run once.
Copter: set yaw-mode in do_loiter mission command
Copter: rename verify_must to verify_nav_command

Perhaps easier to understand if we use the "nav" and "conditional"
command labels
Copter: allow lat/lon to be specified for land
Compass: update parameter description

We do not want people modifying the COMPASS_MOTCT manually
WPNav: make get_stopping_point method public
Copter: bug fix for RTL bearing

Also smooth RTL's initial climb stage by projecting stopping point