NAN doesnt exist on FreeBSD patch by (Rémi Guyomarch <rguyom at pobox dot com>)

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@864 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/eval.c

@@ -28,6 +28,10 @@
 #include <string.h>
 #include <math.h>
 
+#ifndef NAN
+  #define NAN 0
+#endif
+
 #define STACK_SIZE 100
 
 typedef struct Parser{