Set the default total transfer time to 600s.

Retry if we hit a TCP timeout if some data was sent and only error out
when we get an error or no data was sent in the time period.

- mention vmod_std(7)
- HEADER is released and used by vmod_std(7) so put it in its own line.
  The explanation is still needed though.
- for consistency replace leading tabs with spaces
- *fallback* are not strings so avoid mentioning the type
- use ascii characters in vmod_std(7)

And a few style changes from me to vmod_std.rst

Fixes: #1092

CLI to control backend health, rather than rely on probes.

Submitted by:	Federico G. Schwindt

The attached patch is a one-liner for waiter/cache_waiter_ports.c,
the code was referencing sp->t_open where it should have been
sp->t_idle, which was causing assertion failures on idle session
timeouts.

I work with NetBeans, and it insists on this being present.

if sub is null (because it's the contents of a non-existing header),
pretend it's "" instead.

Add a link to the varnishlog man page and the logging chapter in the tutorial

remove -i and -I, add -m and describe it. Simplify the docs. The user only needs to care about -m, really