- Some refactoring that made Find functions possible
   - GetItemPath returns a heap-allocated string
   - subtree update put into a separate function UpdateExpandingTree
   - error() utility function made public
- Find functions are grayed/ungrayed based on context (which fixes
  invalid 'grayed' flag in some localizations).
- InvalidateRect to fix display glitches coming from using
  WM_SETREDRAW.
- English and Polish resource updates (Find dialog box and Find menu
  options, string not found message).