[modula2] Add missing stdbool to testcode

The type bool is now used to represent BOOLEAN.  The C source
must now include <stdbool.h>.

gcc/testsuite/ChangeLog:

	* gm2/types/run/pass/d.c: Add missing include <stdbool.h>.

Signed-off-by: Gaius Mulley <gaiusmod2@gmail.com>

gcc/testsuite/gm2/types/run/pass/d.c

@@ -15,6 +15,8 @@ You should have received a copy of the GNU General Public License along
 with gm2; see the file COPYING.  If not, write to the Free Software
 Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
 
+#include <stdbool.h>
+
 void exit (int);
 
 typedef struct {