Merge branch 'ab/grep-pcre-invalid-utf8'

Update support for invalid UTF-8 in PCRE2.

* ab/grep-pcre-invalid-utf8:
  grep/pcre2: better support invalid UTF-8 haystacks
  grep/pcre2 tests: don't rely on invalid UTF-8 data test

diff --cc Makefile
Simple merge

diff --cc grep.c
Simple merge

diff --cc grep.h
Simple merge