fw att: robustify main loop against non finite numbers and limit error output rate
fw att: pitch ctrl: robustify against non finite numbers
fw att: roll ctrl: robustify against non finite numbers
fw att: yaw ctrl: robustify against non finite numbers
Merge remote-tracking branch 'upstream/master' into fwattrobustify

Conflicts:
	src/modules/fw_att_control/fw_att_control_main.cpp
fw att: add performance counter
makefiles: check for correct arm-none-eabi-gcc version
Merge pull request #975 from PX4/fwattrobustify

Make the fw att controller more robust against infinite input
Removed obsolete flow control example
Allow any GCC 4.7 subversion
Merge branch 'version_check'
Merge branch 'master' of github.com:PX4/Firmware into gps_logging_dual
Better docs in GPS topic
Better docs on log messages
Always log both GPS SNR sets. Assign array IDs by PRN to get a per-satellite unique mapping