Include thornbury header to avoid warning

* Include thornbury header while using thornbury api's,
  without including thornbury header will generate warnings.

Signed-off-by: Manoj Prabhakar Nallabothula <manojprabhakar.n@in.bosch.com>
Reviewed-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D6960

src/lightwood-map/liblightwood-mapbase.c

@@ -37,6 +37,7 @@
  ******************************************************************************/
 
 #include "liblightwood-mapbase.h"
+#include <thornbury/thornbury.h>
 
 typedef enum _MapProperties MapProperties;
 typedef enum _MapSignals MapSignals;