Define NAN -if not already defined- as 0.0/0.0

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@6324 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/eval.c

@@ -35,7 +35,7 @@
 #include <math.h>
 
 #ifndef NAN
-  #define NAN 0
+  #define NAN 0.0/0.0
 #endif
 
 #ifndef M_PI