sim: stdlib.h for abs()

Make sure the files using abs() include stdlib.h for its prototype.
These files were relying on it being included implicitly by others
which isn't guaranteed, and newer toolchains produce warnings.

sim/arm/ChangeLog

@@ -1,3 +1,7 @@
+2021-01-04  Mike Frysinger  <vapier@gentoo.org>
+
+	* iwmmxt.c: Include stdlib.h.
+
 2021-01-04  Mike Frysinger  <vapier@gentoo.org>
 
 	* configure: Regenerate.

sim/arm/iwmmxt.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 <stdlib.h>
 #include <string.h>
 
 #include "armdefs.h"

sim/bfin/ChangeLog

@@ -1,3 +1,7 @@
+2021-01-04  Mike Frysinger  <vapier@gentoo.org>
+
+	* dv-bfin_dma.c: Include stdlib.h.
+
 2021-01-02  Mike Frysinger  <vapier@gentoo.org>
 
 	* interp.c: Change ALIGN to align_up.

sim/bfin/dv-bfin_dma.c

@@ -20,6 +20,8 @@
 
 #include "config.h"
 
+#include <stdlib.h>
+
 #include "sim-main.h"
 #include "devices.h"
 #include "hw-device.h"

sim/testsuite/sim/bfin/ChangeLog

@@ -1,3 +1,7 @@
+2021-01-04  Mike Frysinger  <vapier@gentoo.org>
+
+	* mdma-skel.h: Include stdlib.h.
+
 2015-10-11  Mike Frysinger  <vapier@gentoo.org>
 
 	PR sim/18407

sim/testsuite/sim/bfin/mdma-skel.h

@@ -1,3 +1,4 @@
+#include <stdlib.h>
 #include <string.h>
 
 void _mdma_memcpy (bu32 dst, bu32 src, bu32 size, bs16 mod)