bug#18762: [PATCH] dfa: don't consider RE_DOT_NEWLINE and RE_DOT_NOT_NULL in matching with a bracket expression

[Norihiro Tanaka]

Thanks for the review.

This is a potential bug fix.  However, match_mb_charset function isn't
used in grep and gawk, as DFA treats MBCSET as BACKREF by following code
if `backref' is provided.  Therefore the fix never induces any semantic
change in grep and gawk.

              if (d->states[s].has_mbcset && backref)
                {
                  *backref = 1;
                  goto done;
                }

Essentially, the function is able to be removed.  However, if we regard
DFA as a library,  we should keep it.