Fix typo.

Patch by Jeremy Mordkoff: jlm zazzletech com

Originally committed as revision 10812 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/internal.h

@@ -252,7 +252,7 @@ if((y)<(x)){\
 #define strcat strcat_is_forbidden_due_to_security_issues_use_av_strlcat
 #undef  exit
 #define exit exit_is_forbidden
-#if !(defined(LIBAVFORMAT_BUILD) || defined(FRAMEHOOK_H))
+#if !(defined(LIBAVFORMAT_BUILD) || defined(FFMPEG_FRAMEHOOK_H))
 #undef  printf
 #define printf please_use_av_log
 #undef  fprintf