Fixed no member named 'atop' in global namespace issue for Android NDK compilation

code/StringUtils.h

@@ -42,6 +42,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include <sstream>
 #include <stdarg.h>
+#include <cstdlib>
 
 ///	@fn		ai_snprintf
 ///	@brief	The portable version of the function snprintf ( C99 standard ), which works on visual studio compilers 2013 and earlier.