Rebase changes on upstream master

This brings in many of the changes from the PX4 fork on ATLFLight.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

cmake/configs/nuttx_px4fmu-v2_default.cmake

@@ -83,6 +83,7 @@ set(config_module_list
 	modules/attitude_estimator_q
 	modules/ekf_att_pos_estimator
 	modules/position_estimator_inav
+	modules/ekf2
 
 	#
 	# Vehicle Control

cmake/posix/px4_impl_posix.cmake

@@ -182,6 +182,7 @@ if(UNIX AND APPLE)
 
 else()
 
+
         set(added_definitions
 		-D__PX4_POSIX
 		-D__PX4_LINUX