Remove some useless assignments (the UDPContext is allocated with av_mallocz())

Originally committed as revision 11017 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/udp.c

@@ -309,9 +309,6 @@ static int udp_open(URLContext *h, const char *uri, int flags)
 
     h->priv_data = s;
     s->ttl = 16;
-    s->is_multicast = 0;
-    s->local_port = 0;
-    s->reuse_socket = 0;
     p = strchr(uri, '?');
     if (p) {
         s->is_multicast = find_info_tag(buf, sizeof(buf), "multicast", p);