common: Incorporate upstream changes of regexp.

* regexp/jimregexp.c (regatom): Raise REG_ERR_UNMATCHED_BRACKET when
no matching end bracket.
(regmatch): Fix the end of word check.

Original changes:
Signed-off-by: Steve Bennett <steveb@workware.net.au>

• GnuPG-bug-id: T6455
• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>