Restrict the git hook further to only enforce style in case the found
clang-format binary's version matches to avoid output differences with
different clang-format version.

While at it, move the blacklist reading after the version check to speed
up committing a bit when no local enforcement happens.

Also add a simple script to list formatted files, since the blacklist is
large enough that doing it naively from the shell is too slow.

Change-Id: I0bc05961d262cc6bc91c6efdd1b91994ecfc6940
Reviewed-on: https://gerrit.libreoffice.org/44662Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>