Don't use {} in one-liners

To help track our adoption rate of the new Varnish versions, add the major
version in the default Via header added by us.

It makes sense to default to setting Connection: close for vcl_pipe.
Do this before calling vcl_pipe so it's overrideable.

Fixes #1455

Remove adding of X-Forwarded-For from builtin.vcl and put it into the
C code that runs before vcl_recv.  This makes it more likely that it's
properly set when the user VCL runs.

Fixes: #1454

Mostly an attempt at pointing people that send pull requests on Github
in the right direction.

Move showing of debug counters from 'h' key to 'd' inside a running
varnishstat.

Fixes	#1449

Make sure we do not send a regular "end-chunk" to the
client if the streaming fetch fails.

to reduce code duplication a little bit.

on IMS fetch.