Implement writing RTF to the clipboard (off by default), so that if

Implement writing RTF to the clipboard (off by default), so that if
you enable it text will paste into Word et al in the same font as
PuTTY itself is displaying in. In particular, this will be a fixed-
pitch font, so tables and `ls' and the like will naturally line up.

git-svn-id: svn://svn.tartarus.org/sgt/putty@1373 cda61777-01e9-0310-a592-d414129be87e