Ammended UBlox driver to record SV Info, satelites_visible == satelites used. Info is recorded for all SVs, used or not. Might be useful for GPS debugging.
Merge branch 'master' into gps_fix
Some cleanup of NAV_SVINFO message handler
Merge branch 'master' of https://github.com/PX4/Firmware into gps_fix
Merged GPS info fixes from pigeonhunter
Merge remote-tracking branch 'upstream/master'
General cleanup of /dev/px4io and /dev/px4fmu

- Use distinct common symbols for px4io and px4fmu device files, and use
instead of hardcoded filenames
- Use common symbols defining px4io bits consistently between px4fmu and
px4io builds.