10l: Add #undefs for system free/malloc/realloc, which must be used here.

Originally committed as revision 16794 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/mem.c

@@ -35,6 +35,11 @@
 
 #include "mem.h"
 
+/* here we can use OS dependent allocation functions */
+#undef free
+#undef malloc
+#undef realloc
+
 /* you can redefine av_malloc and av_free in your project to use your
    memory allocator. You do not need to suppress this file because the
    linker will do it automatically */