Merge pull request #251 from yvestroxler/master

Small change in gps-driver (ubx.cpp)
Add support for V for quads with offset arms such as the TBS and SteadiDrone QU4D
HIL bugfixing
Add a mixer file for the V quad
Update the makefile to include the new mixer config.
Finished conversion to C++
Hotfix: GPS MAVLink transmission fixes
Update the quad V values.
Build utility apps -Os to save ROM space.
Pass -g to the link phase for PX4IO the same way we do for FMU
Fix the way that we idle the tone_alarm pin so that the board defines what is the 'safe' state.
Fix an error in a #error
Use the I2C bus number from the board config, not a hardcoded value.
Merge pull request #253 from sjwilks/quad_xv_mode

Add support for quads with offset arms such as the TBS Discovery