Use a more correct value for Pi.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@8024 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

output_example.c

@@ -28,7 +28,7 @@
 #include <math.h>
 
 #ifndef M_PI
-#define M_PI 3.1415926535897931
+#define M_PI 3.14159265358979323846
 #endif
 
 #include "avformat.h"