Serve ESI-includes from a different backend so that we don't race
against when the backend connection is ready for reuse.

Fixes: #1440

it is pass, we may beed the body for retries.

available in vcl_backend_fetch{}

Forgotten in 339b68f9

When starting an ESI subrequest, make sure that the Begin/End headers
are only output once, formatted for ESI.

Fixes: #1441

Missed in 42cec19d

Try to be consistent in the help text across the different tools.

This is mandatory now.

Main reason to duplicate is that it should be visible
in "varnishlog --help". (and friends)

The real condition is that either there is no busyobj or it is in
state BOS_FINISHED, being rapidly dismantled.

The locking of testing that would be to complex and expensive so we
eliminate the assert instead, and strengthen another busyobj related
check a little bit in compensation.

Fixes #1440

Spotted by: Dag

This simplifies the autofoo magic and fixes the manpage installation
on the dist tarball when rst2man was not installed.

Fix the varnishhist documentation include file paths.

Rearrange the varnishhist loop so that we can skip restarts from being
counted and make it more readable.

Without the -b -c options enabled, looking at backend requests becomes
ill-defined. Disable anything but non-esi client requests for
now. This can be extended in the future.