Merge pull request #4 from koenkooi/gps

GPS support  , ignore mwiState->GPS_heading = read16(); from naze , we dont support multipe msp version yet.
mwi: really fix read32()

I compared the read32() function with the one in MultiWii conf and noticed a missing index increment.

This makes GPS work!

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>