added support for the MMS protocol

This patch implements the MMS protocol, by using libmms.  It is quite
experimental: it does not support seeking yet, and it is currently
using synchronous I/O, which causes MPD to hang while waiting for the
server.

src/ls.c

@@ -26,6 +26,12 @@
 static const char *remoteUrlPrefixes[] = {
 #ifdef HAVE_CURL
 	"http://",
+#endif
+#ifdef ENABLE_MMS
+	"mms://",
+	"mmsh://",
+	"mmst://",
+	"mmsu://",
 #endif
 	NULL
 };