Merge declaratio and initialization.

Originally committed as revision 12677 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/mem.c

@@ -140,8 +140,7 @@ void *av_mallocz(unsigned int size)
 char *av_strdup(const char *s)
 {
     char *ptr;
-    int len;
+    int len = strlen(s) + 1;
-    len = strlen(s) + 1;
     ptr = av_malloc(len);
     if (ptr)
         memcpy(ptr, s, len);