Add M_2_PI

include/math.h

@@ -4,7 +4,6 @@
 typedef float float_t;
 typedef double double_t;
 
-// Included to fix mesa issues
 #ifndef M_PI
 #define	M_PI		3.14159265358979323846	/* pi */
 #endif
@@ -16,3 +15,7 @@ typedef double double_t;
 #ifndef M_PI_4
 #define	M_PI_4		0.78539816339744830962	/* pi/4 */
 #endif
+
+#ifndef M_2_PI
+#define M_2_PI		0.63661977236758134308	/* 2/pi */
+#endif