Thx @fgs

Thx @fgs

We're only holding a read lock on the director, but we're updating
the nxt member concurrently. This should be acceptable as a performance
tradeoff - the only consequence is that round-robin is not strictly
going around - it may occasionally skip a backend or hand out the same
multiple times in a row.

the race is:

	thread	code

	A:	rr->nxt %= rr->vd->n_backend;
	// rr->nxt == rr->vd->n_backend - 1
	B:	rr->nxt++;
	// rr->nxt == rr->vd->n_backend
	A:	be = rr->vd->backend[nxt];
	// BOOM

should fix #2024

This is particularly useful when replaying vsl files (-r option).

The new -B option specifies a time factor limiting the speed at which
the log is being read. It can also be halved/doubled using the < and >
keys at runtime.

Actually implement the documented -p option

Make the update delay a double to allow update frequencies of less
than a second.

Add + and - keys to the curses interface to update the refresh
frequency while running.

Show update frequency in the top line.

... for the standard backend timestamps and size.

In usage/documentation, mark those options with <> which are not a
literal string, but rather a placeholder for some value.

Reported by Michel Schuster.

Previously you needed an empty argument (''), which didn't play very
well along sysv init scripts and was not documented.
This should address both problems.

Fixes #2007.

Tunable madvise for file storage

Adresses a new issue mentioned in #2004

Spotted by Foxik on #varnish @ irc.linpro.no.

Fixes #2011

Ref: #2008

We will need it if the body was consumed due to a call to
std.cache_req_body (VRB_Cache).

Analysis and test by daghf.

Fixes #1881.

pipe might receive a complete overhaul in the future but until then
make sure we pass this by default.

Prompted by simon on #varnish @ irc.linpro.no.

The previous attempt to address 1990 was only half-hearted, the fundamental issue
was that we could still fail to set even a 503 response code because we required
workspace to stringify it.

For well known status codes, we now keep constant strings together with the
default reason phrases and emit those.

Add a vtc for the 1990 case.

Fixes #1990

Better fix in the next commit

This reverts commit 83c5ead8.

Related to #2000.

Spotted by:	Régis Leroy

When out of workspace, we dumped the piece of memory at the ws free pointer,
which does not necessarily contain anything sensible in this situation.