urlprotocol: receive a list of protocols from the caller

This way, the decisions about which protocols are available for use in
any given situations can be delegated to the caller.

libavformat/rtmpcrypt.c

@@ -265,7 +265,7 @@ static int rtmpe_open(URLContext *h, const char *uri, int flags)
 
     /* open the tcp or ffrtmphttp connection */
     if ((ret = ffurl_open(&rt->stream, url, AVIO_FLAG_READ_WRITE,
-                          &h->interrupt_callback, NULL)) < 0) {
+                          &h->interrupt_callback, NULL, h->protocols)) < 0) {
         rtmpe_close(h);
         return ret;
     }