gdbsupport/gdb_regex.cc: replace defs.h include with common-defs.h

This was forgotten when gdb_regex was moved from gdb to gdbsupport.

Change-Id: I73b446f71861cabbf7afdb7408ef9d59fa64b804

gdbsupport/gdb_regex.cc

@@ -15,7 +15,7 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
-#include "defs.h"
+#include "common-defs.h"
 #include "gdb_regex.h"
 #include "gdbsupport/def-vector.h"