cosmetic: combine declaration and initialisation

Originally committed as revision 9392 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/cutils.c

@@ -86,8 +86,7 @@ void pstrcpy(char *buf, int buf_size, const char *str)
 /* strcat and truncate. */
 char *pstrcat(char *buf, int buf_size, const char *s)
 {
-    int len;
-    len = strlen(buf);
+    int len = strlen(buf);
     if (len < buf_size)
         pstrcpy(buf + len, buf_size - len, s);
     return buf;