Use GLOBAL_POSITION_INT message type for data updates

[pgiacalo]

Mavelous is using mavlink message type GPS_RAW_INT rather than GLOBAL_POSITION_INT for data updates.

The mavlink web site has this to saw about GPS_RAW_INT...

"The global position, as returned by the Global Positioning System (GPS).
This is NOT the global position estimate of the sytem, but rather a RAW
sensor value. See message GLOBAL_POSITION for the global position
estimate..."

[pchickey]

my fault for not seeing my email straight, this is a dupe of #47 ...