Replace malloc.h with stdlib.h

src/nanovg.c

@@ -16,9 +16,9 @@
 // 3. This notice may not be removed or altered from any source distribution.
 //
 
+#include <stdlib.h>
 #include <stdio.h>
 #include <math.h>
-#include <malloc.h>
 #include <memory.h>
 
 #include "nanovg.h"