RE: icalendar.el bug fix patch

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

> > If we want to keep with this tradition, Emacs should use a separate
> escape sequence for "match any single character including newline".
> 
> I very much agree, for practicality more than tradition. An atomic
> notation is far superior to a modal mechanism.

A single escape is a good thing to have.  That's a
good start.

But it's not either-or.  There's also an advantage,
for users (interactively) and for code, to be able
to use the _same regexp_ to optionally interpret
`.' as match-any-char-including-newline.

IMO we should do both: (1) add an escape for this
and (2) provide a variable and toggle command that
makes `.' match either possibility: any char or
any char except newline.

There are lots of places in existing code that use
predefined regexps, including complex ones.  Letting
these optionally interpret `.' to include a newline
adds functionality.  Even more importantly probably
is letting users use `.' interactively either way.

It's also possible to limit the variable and its
toggling to interactive use (as I explained earlier).
IOW, (optionally) not let it affect regexps in code.