Merge branch 'rs/pcre2-utf'

"git grep --perl-regexp" failed to match UTF-8 characters with
wildcard when the pattern consists only of ASCII letters, which has
been corrected.

* rs/pcre2-utf:
  grep/pcre2: factor out literal variable
  grep/pcre2: use PCRE2_UTF even with ASCII patterns

diff --cc grep.c
Simple merge