stagefright: Include stdlib.h for malloc/free

According to ANSI C, malloc/free are provided by stdlib.h.

Also, string.h is always available according to ANSI C, and provides
the memset function, so there's no need to include it conditionally
for linux only.

This makes the code buildable on OS X, too.

Change-Id: Ie5d1da02158797e7e45dea257cbe3e4996dde4db

media/libstagefright/codecs/common/cmnMemory.c

@@ -21,10 +21,8 @@
 *******************************************************************************/
 #include "cmnMemory.h"
 
-#include <malloc.h>
-#if defined LINUX
+#include <stdlib.h>
 #include <string.h>
-#endif
 
 //VO_MEM_OPERATOR		g_memOP;