bug#9979: 24.0.91; doc string of `save-window-excursion'

[Chong Yidong]

"Drew Adams" <drew.adams@oracle.com> writes:

> The macro does not "preserve" window sizes and contents.  Preserving
> implies that these do not change at any time during the macro call.
> It does not preserve these, but it _restores_ them, after they have
> perhaps been changed by the BODY.  And again, it's important to
> mention that it is only the windows of the selected frame (not other
> frames) that are restored.

I've fixed the docstring.  Thanks.