Also collect in one single place that HASH is the default.

Also update svg and dot files.

Reported on irc by idl0r.

While here also implement -gziplen and -gzipbody.

Fixes #3031.

Fixes #3030.

The behavior described here is old (see cache_fetch.c), but has
not been cleanly documented in the docs.

Fixes: #3024

When executing vcl.show for labels, show the VCL the label points to
instead of asserting.

segments dominate the _.index file.

Relevant for #3023

Be a bit more elaborate on the expected behaviour

Submitted by:	Frederic Lecaille

It's really not obvious, and if it weren't for other tests covering
probes it wouldn't be enough by itself to verify what it needs to.