Reduce developer warnings to make jenkins happy
Always pull the local address of the socket out right away and
log it.  Parallel use of sockets would force us to add locking
and that's simply not worth it.

Also:

Fixes #1376
White-space nit
Document the VCL variables where we define them in generate.py.

Initial doc pulled from vcl.rst

Generate doc/sphinx/reference/vcl_var.rst based on this.
Pull in vcl_var.rst generated by generate.py
Add a simple facility for having variables alias each other and
use it to rename {beresp,resp,obj}.response to *.reason while
still keeping the old ones working.

Use it to also eliminate the already duplicated req.request
and bereq.request (now: *.method)
Add BOOL std.healthy(BACKEND) which can check if any backend is
healthy, rather than have hardcoded variables for
req.backend and bereq.backend's health.
Add INT std.port(IP) which extracts the TCP port number.

By default IP renders as STRING with just the IP number, so if you
want to get the port number there too, you have to do something
like:

	set resp.http.where = client.ip + ":" + std.port(client.ip);

Not too elegant, but it will do.

Remove the "hard-coded" "foo.port" VCL variables.