bug#33414: 27.0.50; inhibit-changing-match-data can be t in syntax-propertize functions, breaking backtrace and looking-at

[Eli Zaretskii]

> From: Pip Cet <pipcet@gmail.com>
> Date: Sat, 17 Nov 2018 13:30:04 +0000
> 
> This was a bit tricky to debug because (backtrace) doesn't work when
> inhibit-changing-match-data is t.  (In emacs -Q, enter
> 
> (let ((inhibit-changing-match-data t)) (backtrace))
> 
> into the *scratch* buffer and evaluate with C-M-x.)

This works on the release branch, so I think it's a regression that
needs to be fixed.

Thanks.