[CLIPBRD] Improvements for the Clipboard Viewer.

[CLIPBRD] Improvements for the Clipboard Viewer.

- Improve the scrolling support for bitmaps, DIBs and text formats.
  This completes the work started in CORE-10679 by Ricardo Hanke.
  Includes scrolling with the keyboard and the mouse wheel.
- Add support for the CF_DSP* clipboard formats, as well as CF_TEXT
  and CF_OEMTEXT.
- Add support for owner-display clipboard format CF_OWNERDISPLAY.
- Realize any palette found in the clipboard (CF_PALETTE) before
  displaying the clipboard data format we want.
- Remove dead code.
- Update the file headers.