Rename open_tcp() to TCP_open() and modify it to open only one socket of

Rename open_tcp() to TCP_open() and modify it to open only one socket of
the appropriate type for the address that was passed in.

Introduce TCP_parse(), which extracts an address and port from a string of
the form "hostname:port", "i.p.v.4:port" or "[i:p:v:6]:port" (where "port"
can be either a decimal number or a service name).

Use TCP_parse() to parse the argument to -a (listen address), -b (backend
address) and -T (telnet address).  Eliminate -p (listen port).

While there, rename a bunch of "fooflag" variables which aren't flags to
"foo_arg".

git-svn-id: svn+ssh://projects.linpro.no/svn/varnish/trunk@872 d4fa192b-c00b-0410-8231-f00ffab90ce4