bug#16777: [PATCH] Revert "grep: DFA now uses rational ranges in unibyte

[Paul Eggert]

> As a point of information, it does happen for gawk.

Could you please say where that happens?  I just now looked at the gawk 
trunk, and the only two places I saw it calling dfaexec 
(helpers/testdfa.c and re.c), it passed a nonnull backref argument.

Obviously this revert does reintroduce the bug with [\]-\]] that you 
mentioned with Awk regular expressions.  It reintroduces similar bugs 
for GNU grep.  At the very least we should fix that. I'll follow up with 
a patch.