CTFE: Pointer cast wrong-code bug

This is a severe, obvious bug -- the pointer offset was ignored. So that  &var[5]  was becoming &var[0]  !

But as far as I know, the bug cannot be triggered at the moment, because this pointer type-painting is normally done by the constant folding in optimize.c.

This was causing the test suite to fail on Win32 when using CTFE to do const folding.