bug#15251: 24.3.50; do-auto-fill "continues" comment from inside a string

[Dmitry Gutov]

Version: 24.4

On 30.09.2013 21:27, Stefan Monnier wrote:
> > Stefan, can we consider `syntax-ppss' fast enough at this point?
>
> If comment-use-syntax is t, yes.

Done, in 114486.

I kept the rest of `comment-beginning' definition, in case 
non-syntax-table-using comments can still be font-locked in some modes.

Also, `comment-use-global-state' looks like a better var to base the 
choice on, semantically, but it's not auto-detected, and it's only used 
in `comment-search-forward'.