bug#24869: 26.0.50; Emacs should not force lower FD limit on subprocesses

[Paul Eggert]

Brendan O'Dea wrote:
> A potential fix would be to stash the initial limit before changing it, and
> then restore that limit in child_setup().

Thanks, I did that, and am closing the bug.

> My inclination however would just be to revert that entire change: AFAICT it
> merely moves the problem from emacs crashing under some aberrant behaviour, to
> emacs no longer working under that same behaviour due to system calls randomly
> failing with EMFILE.

Crashing is quite bad. I'd rather have Emacs report a reasonable diagnostic 
instead. If Emacs is not doing that, we should fix it.