GPS NMEA parsing and NAV code

• Parsing of popular NMEA sentences to string buffers
• Distance functions for GPS coordinates (Haversine, and law of cos)
• Bearing formulas and functions
• Conversion to decimal degrees
• misc conversion functions for display

This code allows the user to parse GPS data froma single buffer, and put the data in the appropriate buffers.

It also allows the user to perform navigation calculations using accurate forumulas such as the Haversine or a simpler formula like law of cos. Bearing forumulas are also included, as are some common conversions to decimal degrees and some other misc conversions.

This code is for dsPIC, however it is easily ported to PIC32 and other platforms.