bug#27350: 25.2; Make `inhibit-compacting-font-caches' customizable

[Drew Adams <drew.adams@oracle.com>]

> This variable is a "fire escape": it only exists because we were
> unable to fix some of the situations where the slow-down happens (in
> other cases changing the end-user font configuration fixed the
> problem).  Ideally, it will some day go away.  Making it a defcustom
> and documenting it will make removing it harder.

I see.  In that case, agreed.  Perhaps NEWS should characterize it
that way, instead of nearly suggesting that it is a user variable:

 "Set this variable to a non-nil value to speed up display of
  ^^^^^^^^^^^^^^^^^
  characters using large fonts, at the price of a larger memory
  footprint."

> So no, I don't think we should do what you suggest, leaky postings on
> Stackexchange notwithstanding.  (And those postings actually harm the
> project, because all such problems should be reported as bugs,
> allowing us to investigate as many of these problems as possible, and
> hopefully helping us eventually find the culprit.  "Solving" them on
> Stackexchange avoids bringing more of such problems to our attention.)

I'm glad I brought it to your attention, in that case. ;-)

You know where to find the person with the problem, if you
want more info about that specific case.

And you can also consider addressing the referenced "GitHub
discussion thread" (I haven't looked at it), either to get
further info about specific problems encountered or to let
folks there know that you would prefer that they raise an
Emacs bug.

Both of those references should presumably help you gather
info about "as many of these problems as possible".