Allow --no-verify to bypass commit-msg hook

Allow --no-verify to bypass commit-msg hook

At the moment the --no-verify switch to "git commit" instructs it to
skip over the pre-commit hook. Here we teach "git commit --no-verify"
to skip over the commit-msg hook as well. This brings the behaviour
of builtin-commit back in line with git-commit.sh.

Signed-off-by: Wincent Colaiuta <win@wincent.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>