[cpp] Remove elementSize from cpp.Pointer since it causes issues with forward declared types.

std/cpp/Pointer.hx

@@ -24,8 +24,6 @@
 @:coreType
 extern class Pointer<T> extends ConstPointer<T> implements ArrayAccess<T>
 {
-   public var elementSize(default,never):Int;
-
    @:analyzer(no_simplification)
    public var ref(get,set):T;