bug#21333: 25.0.50; window-size-change-functions not called after mini-window resize

[martin rudalics]

>> Looks like bug #830
>>
>> 23.0.60; window-size-change-functions sometimes not called
>>
>> in action.
>
> Agreed, that appears to be the same bug. (I appear to have searched
> for window-size-changed-functions when reporting this, not
> window-size-change-functions). I don't know what the Emacs policy is
> on merging bug reports, but we probably should.

I just merged them.  `window-size-change-functions' is a Cinderella of
our hooks.  Nobody really knows when it should be used, me included.
Markus considered it necessary for ‘linum-mode’ but apparently changed
his mind later.  The only "real" user is probably ‘follow-mode’.

>> Your patch looks fine to me.  I'd suggest to postpone installing it until
>> your paperwork is complete.  OK?
>
> Absolutely. I must admit I was expecting a discussion first, so I
> decided to send this right away to get it over with :-)

It might be worth pursuing the simpler solution to set
FRAME_WINDOW_SIZES_CHANGED "only" in window_resize_apply because
conceptually _all_ window size changes "must" pass through that
function.  I never checked the truth of that "must" but am quite
confident that anything else would result in a bug.  There is one
prominent exception from this rule - `delete-other-windows' when the
sole remaining window is a leaf window.  That was my last remedy when I
tested the resize code and `window-resize-apply' failed for whatever
reason.  C-x 1 reliably got me out of that mess.

martin