Remove duplication to some extent by moving common return keywords
to a separate paragraph.

Add fail and vcl(label) keywords

Fix some typos

Since we decoupled the client and backend side, restarts are completely
unrelated to backend requests.

Related to #2405

req->restarts only gets incremented in cnt_restart, so it will never
exceed max_restarts here.

Related to #2405

max_restarts is the number of allowed restarts

Related to #2405

On platforms where umem is available (specifically Solaris descendents), we want
to make umem the default allocator for performance reasons and also for vtc coverage
while still keeping the malloc type as fallback option.

This reverts commit 766dee06.

Conflicts:
	bin/varnishd/mgt/mgt_main.c

varnishd sources now use cache_priv.h as primary #include, and that
includes cache.h, rather than the other way around.

In varnishtest, varnish checks now use -expect PATTERN OP NUMBER
PATTERN being a glob pattern (see fnmatch(3)).

Make all vtc checking for SMA counters stevedore-type agnostic by matching
on SM?

VDI_ functions out of $ABI VRT.

life easier for patch in the pipeline.