If the ban lurker finds a busy object, skip the object and defer the
checking to a later pass.

No test case because it is very timing sensitive (but see the trac bug
report for a VTC-file that mostly triggers it on the 3.0 branch only)

Fixes: #1162

There is a short window of opportunity between HSH_Insert() and
HSH_Unbusy(), where the locks are released and the expiry thread can
try to expire an object that is still busy (for objects with very
short TTL). This patch makes the expiry thread check for busy objects
and wait if the head of the binheap is busy.

No test case as the window is too small.

Fixes: #1150

An attempt to nuke a busy object will end in assertion.

objects.

This avoids a memory race on the n_sess counter, which can lead to
excessive session object allocation. Keeping the counters of in use
and released separate allows the acceptor to continue to run lockless.

Fixes: #897

Patch by: tnt

Fixes	#1100

Conflicts:

	bin/varnishd/cache_fetch.c
	bin/varnishd/cache_panic.c

Conflicts:

	bin/varnishd/cache/cache_esi_fetch.c
	bin/varnishd/cache_fetch.c
	bin/varnishd/cache_gzip.c

Submitted by:	Martin
Fixes		#1140

Fixes a case where we might get a cache hit even though hash_always_miss is set.

Fixes: #1073

Fixes #1035

Implemented more or less as described in the pcrejit(3) manpage, and
adds some compatibility defines for use with older pre-8.20 libraries
that do not have this functionality.

Fixes: #1080

Fixes #1122

Fixes #1069

argument to a printflike function.

Needed to test #1123