contrib/ChangeLog:
* git-commit-mklog.py: Do not parse -b argument.
Pass mklog_args as json environment variable.
* mklog.py: Parse GCC_MKLOG_ARGS and append it to sys.argv.
* prepare-commit-msg: Do not append GCC_MKLOG_ARGS to args.
The argument can be used for addition of Co-Authored-By lines
with --trailer='Co-Authored-By=Mona Lisa Octocat <mona@github.com>'.
contrib/ChangeLog:
* gcc-git-customization.sh: Wrap $@ in quotes.
* git-commit-mklog.py: Add new argument --co.
* mklog.py: Skip the Co-Authored-By lines.
