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/input_stream.c

@@ -29,6 +29,10 @@
 #include "input_curl.h"
 #endif
 
+#ifdef ENABLE_MMS
+#include "input_mms.h"
+#endif
+
 #include <glib.h>
 #include <assert.h>
 
@@ -40,6 +44,9 @@ static const struct input_plugin *const input_plugins[] = {
 #ifdef HAVE_CURL
 	&input_plugin_curl,
 #endif
+#ifdef ENABLE_MMS
+	&input_plugin_mms,
+#endif
 };
 
 static const unsigned num_input_plugins =