[meta, x64] Use _PtrAdd() to calculate memory offsets

[Infocatcher]

Example from SearchReplace.js:

function RectToArray(lpRect, rcRect)
{
  rcRect.left=AkelPad.MemRead(_PtrAdd(lpRect, 0) /*offsetof(RECT, left)*/, 3 /*DT_DWORD*/);
  rcRect.top=AkelPad.MemRead(_PtrAdd(lpRect, 4) /*offsetof(RECT, top)*/, 3 /*DT_DWORD*/);
  rcRect.right=AkelPad.MemRead(_PtrAdd(lpRect, 8) /*offsetof(RECT, right)*/, 3 /*DT_DWORD*/);
  rcRect.bottom=AkelPad.MemRead(_PtrAdd(lpRect, 12) /*offsetof(RECT, bottom)*/, 3 /*DT_DWORD*/);
  return rcRect;
}