eval: include libavutil/mathematics.h for NAN and M_PI

Originally committed as revision 19613 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/eval.c

@@ -33,17 +33,10 @@
 #include <string.h>
 #include <math.h>
 
+#include "libavutil/mathematics.h"
 #include "avcodec.h"
 #include "eval.h"
 
-#ifndef NAN
-  #define NAN 0.0/0.0
-#endif
-
-#ifndef M_PI
-#define M_PI 3.14159265358979323846
-#endif
-
 typedef struct Parser{
     int stack_index;
     char *s;