Fix a typo in sdp_write_header(): change "IPV4", which is not a valid

network address type, to "IP4".

Originally committed as revision 14465 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/sdp.c

@@ -56,7 +56,7 @@ static void dest_write(char *buff, int size, const char *dest_addr, int ttl)
 static void sdp_write_header(char *buff, int size, struct sdp_session_level *s)
 {
     av_strlcatf(buff, size, "v=%d\r\n"
-                            "o=- %d %d IN IPV4 %s\r\n"
+                            "o=- %d %d IN IP4 %s\r\n"
                             "t=%d %d\r\n"
                             "s=%s\r\n"
                             "a=tool:libavformat " AV_STRINGIFY(LIBAVFORMAT_VERSION) "\r\n",