bug#24315: 25.1.50; re-search-forward errors with "Variable binding depth exceeds max-specpdl-size"

[npostavs]

# the new bug will be about the specdl error
clone 24315 -1
# this bug is about the bad regex in icalendar
retitle 24315 icalendar--read-element uses inefficient regexp
quit

peder@klingenberg.no (Peder O. Klingenberg) writes:
>  Updated patch attached.
>
[...]
> Subject: [PATCH] Avoid crash in icalendar--read-element
>
> * lisp/calendar/icalendar.el (icalendar--read-element): Stop crashing
> when parsing overly long event descriptions.  (Bug#24315)

Patch looks good, though I think the description shouldn't say "crash",
since the problem is a regex stack overflow, which is just a normal
Emacs error (I've figured out the reason why it's triggering
max-specpdl-size instead of regex stack overflow in master, and will
address it in a separate bug).