Expose WebPMalloc() in addition to WebPFree()

and use it at various places, including for WebPData.

This is an API change!

Change-Id: Ic041323a1179c465292a4f981a86c4c34635d243

src/utils/utils.c

@@ -216,9 +216,14 @@ void WebPSafeFree(void* const ptr) {
   free(ptr);
 }
 
-// Public API function.
+// Public API functions.
+
+void* WebPMalloc(size_t size) {
+  return WebPSafeMalloc(1, size);
+}
+
 void WebPFree(void* ptr) {
-  free(ptr);
+  WebPSafeFree(ptr);
 }
 
 //------------------------------------------------------------------------------