STRING_LIST to STRING for error messages.

Fixes #2510

Submitted by:	klean@github

Give procedures proper data structures and stick the VCL methods into
the symbol table up front and GC a lot of small hacks and workarounds.

Timing out an H/2 session needs to take into account any active streams
being processed.

that VCL_ENUM have canonical pointers.

involved versions of same with a simple pointer comparison.

by various standardsbodies.

Going forward these macros will all be named 'v_[a-z_]*_' and only
vdef.h gets to define them.

Renames:
	__match_proto__()		->	v_matchproto_()
	__v_printflike()		->	v_printflike_()
	__state_variable__()		->	v_statevariable_()
	__unused			->	v_unused_
	__attribute__((__noreturn__))	->	v_noreturn_

As a side-effect of the last one, the rule that "vdef.h" be the
first non-<...> include in .c files, possibly via a subsystem
.h (such as vct.h) needs to be enforced harder.

(autocraps "config.h" still needs to go before <...> includes)

Fixes #2508

Fixes #2506

it was deprecated since varnish 5.1.

motivated by the bereq.retries cleanup, see #2405

the be->vsc under backend mtx.

Fixes #2505

Also add asserts for the references held in req->objcore and
req->stale_oc.

The test case for #1807 catches this bug after adding the asserts.

Fixes: #2502

Fixes: #1772

With VTP_Close now being capable of dealing with STOLEN connections, we
no longer need to VTP_Wait for them prior to close.

The change from shutdown(.., SHUT_WR) to shutdown(.., SHUT_RDWR) is
required to make it trigger a waiter event.

This test case should not rely on
first_byte_timeout/between_bytes_timeout.

This issue is hidden by the fix in the previous commits, so we cannot test
for it directly any more. Applying this patch to
fa388439 exposes the "Constructor not found".

Fixes #2498

When we are looking for ! SYM_NONE and find ! SYM_NONE, do not
return the symbol we found.

The semantics of (kind != SYM_NONE && sym->kind != kind) are
inclusive because the next conditional is not true for this case.

Ref: 9d81a71a

Fixes: #2497

The second time around, we force a fresh connection.

The VCL user may choose to do 'return (retry);' in vcl_backend_error{}
if further attempts are deemed warranted.

Fixes: #2135