output/raop: fallback for g_set_error_literal()

This function was added in GLib 2.18.  Make the plugin compatible with
older GLib versions.

src/glib_compat.h

@@ -80,4 +80,15 @@ g_uri_parse_scheme(const char *uri)
 
 #endif
 
+#if !GLIB_CHECK_VERSION(2,18,0)
+
+static inline void
+g_set_error_literal(GError **err, GQuark domain, gint code,
+		    const gchar *message)
+{
+	g_set_error(err, domain, code, "%s", message);
+}
+
+#endif
+
 #endif

src/output/raop_output_plugin.c

@@ -20,6 +20,7 @@
 #include "output_api.h"
 #include "mixer_list.h"
 #include "raop_output_plugin.h"
+#include "glib_compat.h"
 
 #include <glib.h>
 #include <unistd.h>