Clean up gmp-utils.h includes

gmp-utils.h includes "defs.h", but normally the rule in gdb is that
the .c files include this first.  This patch changes this code to
match the rest of gdb.

gdb/gmp-utils.c

@@ -15,6 +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 "gmp-utils.h"
 
 /* See gmp-utils.h.  */

gdb/gmp-utils.h

@@ -20,8 +20,6 @@
 #ifndef GMP_UTILS_H
 #define GMP_UTILS_H
 
-#include "defs.h"
-
 /* Include <stdio.h> and <stdarg.h> ahead of <gmp.h>, so as to get
    access to GMP's various formatting functions.  */
 #include <stdio.h>

gdb/unittests/gmp-utils-selftests.c

@@ -17,6 +17,7 @@
    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 "gmp-utils.h"
 #include "gdbsupport/selftest.h"