Clearly label EAGAIN as being the UDP checksum error that it is

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@3157 65c4cc65-6c06-0410-ace0-fbb531ad65f3

rtp.c

@@ -411,6 +411,9 @@ struct ast_frame *ast_rtp_read(struct ast_rtp *rtp)
 
 	rtpheader = (unsigned int *)(rtp->rawdata + AST_FRIENDLY_OFFSET);
 	if (res < 0) {
+		if (errno == EAGAIN)
+			ast_log(LOG_NOTICE, "RTP: Received packet with bad UDP checksum\n");
+		else
 			ast_log(LOG_WARNING, "RTP Read error: %s\n", strerror(errno));
 		if (errno == EBADF)
 			CRASH;