xwayland: Include missing config.h

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
diff --git a/compositor/xwayland.c b/compositor/xwayland.c
index 26eda20..9fa7600 100644
--- a/compositor/xwayland.c
+++ b/compositor/xwayland.c
@@ -24,6 +24,8 @@
  * SOFTWARE.
  */
 
+#include "config.h"
+
 #include <signal.h>
 #include <sys/socket.h>