Fine-tuning the behavior of `org-yank'.

Fine-tuning the behavior of `org-yank'.

Org-mode's `org-yank' command is used as a replacement for the normal
`yank' command.  It differs by giving special treatment to subtrees or
sets of subtrees when yanking them, by adjusting the level to fit the
outline, and by folding the trees after the yank.

This patch does fine-tune this behavior.

First of all, if any prefix argument is given to the command, it
immediately hands over the action to the standard `yank' command.  In
particular, you can use `C-u C-y' to yank as-is, with the only minor
side effect that the cursor will end up at the beginning of the yanked
text.

Secondly, the folding of the yanked trees will only happen if there is
no text directly after the insertion point that would be swallowed by
the folding process.  This was confusing in the past and is much
better now, with a message announcing that folding has been
suppressed.