Least Recently Used stack based kill-ring manipulation

[Le Wang]

I always thought the way the kill-ring works was less than intuitive.
Instead of moving around in a ring, it would be more useful to me if
the stuff I yank are moved to the top of a stack.

This fits my usage scenarios better.  I occasionally yank stuff far
away from each other in the ring, which is difficult with the default
yank functions.  And I never refer to the stuff I I yanked long ago.

This is similar to how windows are ordered in Windows.  So here it is.

http://www.emacswiki.org/cgi-bin/emacs/LRU-yank.el