Add public wxDegToRad() and wxRadToDeg() functions.

Define these functions just once in wx/math.h instead of duplicating them in a
dozen of places.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76555 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/math.h

@@ -133,6 +133,10 @@ inline int wxRound(double x)
     #endif
 }
 
+// Convert between degrees and radians.
+inline double wxDegToRad(double deg) { return (deg * M_PI) / 180.0; }
+inline double wxRadToDeg(double rad) { return (rad * 180.0) / M_PI; }
+
 #endif /* __cplusplus */