Problem: The 'grepformat' option is global option, but it would be
useful to have it buffer-local, similar to 'errorformat' and
other quickfix related options (Dani Dickstein)
Solution: Add the necessary code to support global-local 'grepformat',
allowing different buffers to parse different grep output
formats (glepnir)
fixes: vim/vim#17316closes: vim/vim#173157b9eb6389d
Co-authored-by: glepnir <glephunter@gmail.com>