Update Killing chapter of manual for Emacs 24 clipboard changes.

Update Killing chapter of manual for Emacs 24 clipboard changes.

* doc/emacs/frames.texi: Move Cut and Paste node and subnodes into
killing.texi, except Mouse Commands and Word and Line Mouse.

* doc/emacs/killing.texi (Killing, Deletion and Killing, Killing by Lines)
(Other Kill Commands, Kill Options): Copyedits.
(Deletion and Killing, Kill Ring): Kill/yank now use clipboard.
(Yanking): Move yank-excluded properties discussion here.
(Cut and Paste): Move from frames.texi.  Update subnodes to
describe x-select-enable-clipboard case.