AP_Math: rename get_bearing() to get_bearing_cd() to make units obvious

libraries/AP_Math/AP_Math.h

@@ -37,7 +37,7 @@ float get_distance(const struct Location *loc1, const struct Location *loc2);
 int32_t get_distance_cm(const struct Location *loc1, const struct Location *loc2);
 
 // return bearing in centi-degrees between two locations
-int32_t get_bearing(const struct Location *loc1, const struct Location *loc2);
+int32_t get_bearing_cd(const struct Location *loc1, const struct Location *loc2);
 
 // see if location is past a line perpendicular to 
 // the line between point1 and point2. If point1 is 

libraries/AP_Math/location.cpp

@@ -61,7 +61,7 @@ int32_t get_distance_cm(const struct Location *loc1, const struct Location *loc2
 }
 
 // return bearing in centi-degrees between two locations
-int32_t get_bearing(const struct Location *loc1, const struct Location *loc2)
+int32_t get_bearing_cd(const struct Location *loc1, const struct Location *loc2)
 {
 	int32_t off_x = loc2->lng - loc1->lng;
 	int32_t off_y = (loc2->lat - loc1->lat) / longitude_scale(loc2);