Copter: remove unused RADX100 definition

The real purpose of this small change is to kick off the autobuilder for
the AC3.1.1 release.

ArduCopter/defines.h

@@ -303,8 +303,8 @@
 #define DATA_EPM_ON                     46
 #define DATA_EPM_OFF                    47
 #define DATA_EPM_NEUTRAL                48
-// RADIANS
-#define RADX100 0.000174532925f
+
+// Centi-degrees to radians
 #define DEGX100 5729.57795f