VC check-in and window configuration

[Andre Spiegel]

A user suggested that C-x v v, when used for check-in, should remember
the current window configuration and restore it after the user typed
C-c C-c in the *VC-log* buffer.  This is not the first time this
suggestion comes up, but I remember vaguely that we have discussed
this before.  Back then, the consensus seemed to be that it's just not
possible to decide what is the "right thing" to do in this situation,
and that things might as well be left as they are.

But that's only a vague memory.  Other than that, I think the idea is
perfectly reasonable, so if I hear no objections, I'm going to install
such a change.