FMUv2: switch debug console and 2nd GPS

this allows a normal GPS cable to be used for the 2nd GPS, making
dual-GPS setups easier
Fixed warning
Merge branch 'master' of github.com:PX4/Firmware
Revert "Fixed warning"

This reverts commit 3639c7ae91f5226b71cdba8d8cc98eae4bba7e07.
mc_att_control: hotfix, memset all structs to zeroes on start, fixes garbage in actuator controls 4..8
Reduce excessive stack sizes on main OS stacks. This has been tested on mavlink_beta, but needs more careful testing.
Merge branch 'stack_reduce' of https://github.com/PX4/Firmware into helen_ardrone