don't use dolist to add entries to auto-mode-alist

See #110 and #111.
don't use EMACS environment variable

The EMACS environment variable is usually defined by tramp to the value "t".
Replace the variable name with EMACS_BIN to avoid build failure.
git-commit-setup-hook: make better use of :options Custom property
Merge branch 'master' into next

Conflicts:
	Makefile
	git-commit-mode.el