Move the body of cli_quote() to vsb_quote() and give it a, presently
unused, "how" argument flag.

We currently have far too many "quote this string properly" implementations
in varnish, hopefully, this will replace most of them.

Once this stabilizes, vsb_quote() will be contributed back to FreeBSD.



git-svn-id: http://www.varnish-cache.org/svn/branches/2.0@3704 d4fa192b-c00b-0410-8231-f00ffab90ce4