Dispose when refcount goes to zero.
Private objcores for pipe neither want nor need a boc, so make it optional.

I don't think this will be necessary at the end state, but it makes
the transformation easier.

now that we have a struct boc.

(struct boc) and "the backend fetch context" (struct bereq).

WS_Assert allows the workspace to be full in its check that `ws->f <= ws->e`.
WS_Reset does not honor this; if a snapshot was taken of a full workspace, and
that snapshot is reverted with WS_Reset, we panic.

This issue was identified by Jozef Hatala <jozef@fastly.com>

This (useless) range request is send by Chrome with HTML5 Video.
This was not working correctly in 4.0 and was fixed somewhere
in master.

Discussed with phk@.  Fix confirmed by geoff@.

Fixes #1844.

Fixes previous commit. Sigh.

Broken in 9bb8f962.
Committed solution proposed by phk@, discussed with phk@ and martin@.

Fixes #1845.

Discussed with mithrandir@.

Prompted by #1845.  I'm not entirely sure whether some literals like
"1.00 " should be accepted but that's the current behaviour.

into the macro-table.

Instead of counting the references, the VCL keeps track of them with up
to 31 characters in the description. It is the VMOD's responsibility to
keep track of the opaque struct vclref * and provide a meaningful user-
friendly description.

By the time we decide to switch to a VCL, it must be warm and usable.
The deprecated VCL_EVENT_USE should not get in the way.

Don't update the state of the VCL to warm if it failed, and don't start
the child if the active VCL failed to warm up.

The implementation is similar to the load/discard dance when a load
fails. New VGC functions are introduced iff the VCL has at least one
VMOD handling events.

The generated code looks like this:

	static unsigned vgc_inistep;
	static unsigned vgc_warmupstep;

	...

	static int
	VGC_Load(VRT_CTX)
	{
		...
	}

	static int
	VGC_Discard(VRT_CTX)
	{
		...
	}

	static int
	VGC_Warmup(VRT_CTX, enum vcl_event_e ev)
	{

		vgc_warmupstep = 0;

		/* 4 */
		if (Vmod_debug_Func._event(ctx, &vmod_priv_debug, ev))
			return (1);
		vgc_warmupstep = 4;

		return (0);
	}

	static int
	VGC_Use(VRT_CTX, enum vcl_event_e ev)
	{

		/* 4 */
		if (Vmod_debug_Func._event(ctx, &vmod_priv_debug, ev))
			return (1);

		return (0);
	}

	static int
	VGC_Cooldown(VRT_CTX, enum vcl_event_e ev)
	{
		int retval = 0;

		/* 4 */
		if (vgc_warmupstep >= 4 &&
		    Vmod_debug_Func._event(ctx, &vmod_priv_debug, ev) != 0)
			retval = 1;

		return (retval);
	}

	static int
	VGC_Event(VRT_CTX, enum vcl_event_e ev)
	{
		if (ev == VCL_EVENT_LOAD)
			return(VGC_Load(ctx));
		if (ev == VCL_EVENT_WARM)
			return(VGC_Warmup(ctx, ev));
		if (ev == VCL_EVENT_USE)
			return(VGC_Use(ctx, ev));
		if (ev == VCL_EVENT_COLD)
			return(VGC_Cooldown(ctx, ev));
		if (ev == VCL_EVENT_DISCARD)
			return(VGC_Discard(ctx));

		return (1);
	}

However, if there are no VMODs handling events, no new functions shall
be generated, leading to code looking like this:

	static unsigned vgc_inistep;
	static unsigned vgc_warmupstep;

	...

	static int
	VGC_Load(VRT_CTX)
	{
		...
	}

	static int
	VGC_Discard(VRT_CTX)
	{
		...
	}

	static int
	VGC_Event(VRT_CTX, enum vcl_event_e ev)
	{
		if (ev == VCL_EVENT_LOAD)
			return(VGC_Load(ctx));
		if (ev == VCL_EVENT_DISCARD)
			return(VGC_Discard(ctx));

		(void)vgc_warmupstep;
		return (0);
	}

It is also possible to convey a message to the CLI. In case of a failure
the VCL is cooled down. VCL_Load may now fail with either CLIS_PARAM or
CLIS_CANT.

concurrent -C tests don't collided.

Problem spotted by:	fgs

Fixes:	#1802