* remember push errors in the context
* also fail additional pushes once we saw an error

Try to fail requests as early as possible. Otherwise just calling VDP
functions after an error is a noop.

Fixes #2618

suncc implements the inline functions from cache.h using it

This includes building the fuzzer to avoid code rot, but exercising
the fuzzer will be done elsewhere.

As WS_Reset() clears the overflow marker, the correct order for
resetting and marking an overflow is WS_Reset(); WS_MarkOverflow();

Fixes the last seemingly obscure bit of #2645

Conflicts:
	doc/sphinx/reference/vcl_var.rst (beresp.filters)

list of VCLs" vs. "Do things with VCLs on list"

Ref: #2645

Should we plan to phase out synthetic() ?

Thank you to @martin-uplex for the review

Conflicts:
	bin/varnishd/cache/cache.h

Arguably, this is a breaking change in $ABI vrt.

Supress terminal responses by default and hope they look right.

Return HTC_S_OVERFLOW if exceeded.

This is a quick-fix for #2624, where we close the connection if a client
exceeds MAX_FRAME_SIZE. More proper handling with draining the rest of
the frame for the specific frames types that allow it (rfc7540 section
4.2) to come later.

Fixes: #2624

Fixes #2617