bug#358: dabbrev-abbrev-char-regexp

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

> > Of course, the problem here is that we are talking about expanding
> > `yes-or-no-p', which in Lisp is a Lisp symbol.  It would probably
> > be better to talk about using dabbrev in another context, besides
> > Lisp.  Then it would be clearer that we are talking only about
> > symbol vs word syntax.
> 
> As in, use a C example instead?
> 
> For instance, suppose the current buffer is in `c-mode'.  If this
> variable is nil or \"\\\\sw\\\\|\\\\s_\", then expanding
> `debug_print_in_' looks for a symbol starting with
> `debug_print_in_'.  If you set this variable to \"\\\\sw\", that
> expansion looks for a word prefixed with `in_' (e.g., it would
> match `in_range', but not `in_close_range').  If expanding
> `debug_print_in' it would look for a word starting with
> `in' (e.g. `integer')."

Yep. Thx.