Merge remote-tracking branch 'qatar/master'

* qatar/master:
  configure: Add -Wno-format-zero-length to CFLAGS.
  udp: Receive on the remote port number, if no local port is set

Merged-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -3035,6 +3035,7 @@ check_cflags -Wdeclaration-after-statement
 check_cflags -Wall
 check_cflags -Wno-parentheses
 check_cflags -Wno-switch
+check_cflags -Wno-format-zero-length
 check_cflags -Wdisabled-optimization
 check_cflags -Wpointer-arith
 check_cflags -Wredundant-decls

libavformat/udp.c

@@ -444,7 +444,7 @@ static int udp_open(URLContext *h, const char *uri, int flags)
             goto fail;
     }
 
-    if (s->is_multicast && (h->flags & AVIO_FLAG_READ))
+    if ((s->is_multicast || !s->local_port) && (h->flags & AVIO_FLAG_READ))
         s->local_port = port;
     udp_fd = udp_socket_create(s, &my_addr, &len);
     if (udp_fd < 0)