regex: fix false multibyte matches in some regular expressions See <http://sourceware.org/bugzilla/show_bug.cgi?id=13637> and <http://sourceware.org/ml/libc-alpha/2012-02/msg00521.html>. * lib/regex_internal.c (re_string_skip_chars): Fix miscomputation of remain_len that may cause incomplete multi-byte character and false match.