Replace the malloc.h header with stdlib.h.

--- src/example/allocate_module.c.orig	Mon Nov  3 23:23:33 2014
+++ src/example/allocate_module.c	Mon Nov  3 23:23:52 2014
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#include <malloc.h>
+#include <stdlib.h>
 
 #if UNIT_TESTING
 extern void* _test_malloc(const size_t size, const char* file, const int line);
