This "regex_t" in grep_opt has not been used since f9b9faf6f8a (builtin-grep: allow more than one patterns., 2006-05-02),
we still use a "regex_t" for compiling regexes, but that's in the
"grep_pat" struct".
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>