lavf/udp: warn in case the circular_buffer_size or overrun_nonfatal options are not supported

They are only supported if pthread is available.

libavformat/udp.c

@@ -496,6 +496,10 @@ static int udp_open(URLContext *h, const char *uri, int flags)
             /* assume if no digits were found it is a request to enable it */
             if (buf == endptr)
                 s->overrun_nonfatal = 1;
+            if (!HAVE_PTHREAD_CANCEL)
+                av_log(h, AV_LOG_WARNING,
+                       "'overrun_nonfatal' option was set but it is not supported "
+                       "on this build (pthread support is required)\n");
         }
         if (av_find_info_tag(buf, sizeof(buf), "ttl", p)) {
             s->ttl = strtol(buf, NULL, 10);
@@ -514,6 +518,10 @@ static int udp_open(URLContext *h, const char *uri, int flags)
         }
         if (av_find_info_tag(buf, sizeof(buf), "fifo_size", p)) {
             s->circular_buffer_size = strtol(buf, NULL, 10)*188;
+            if (!HAVE_PTHREAD_CANCEL)
+                av_log(h, AV_LOG_WARNING,
+                       "'circular_buffer_size' option was set but it is not supported "
+                       "on this build (pthread support is required)\n");
         }
         if (av_find_info_tag(buf, sizeof(buf), "localaddr", p)) {
             av_strlcpy(localaddr, buf, sizeof(localaddr));