new improved probability of getting the VSL out.

That obscured problems in cleanup

The script lacked a logexpect -wait at the end telling it to actually
wait for the required log content.

Added a new rule to match first on an actual retry backend transaction
and match the header set/unset/set tests on that vxid.

Check if system has closefrom(2) and use that where available

represents the current limit.

Also don't call it every iteration of the loop.

Avoids memcpy/free if the buffer was dynamic.

Unbreaks distcheck.

Trips up my syntax highlighting.

To get this into the normal Sphinx build, move it to bin/varnishstat/
(where it feels like it belongs the most), and use our normal build flow for man
pages.

We don't maintain any history, and the man page is covered by the
distribution copyright.