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

This was already called and has not been any changes since then.

If we don't have enough space for the requested size, don't xxxassert,
just mark the overflow and return 0.

Discussed with daghf@ and dridi@.

changing the storage list.

Fixes: #1839

This reverts commit f4895da5, there are
pending changes in semantics in VCL temperature that conflict with this
commit.

Dridi:  Not XXX comments

the fetching busyobj is no longer.

sequence.

rather than have the fetch code make a blanket ban.

The two functions are separated in order to have self-documenting
signatures because one class of events is (or will be) allowed to
fail while the other MUST be failsafe.

This paves the way towards failing VCL_EVENT_WARM events in VMODs. If
setting the temperature fails, we may need to carry a message back to
the CLI and other bits of context.

Make a clear distinction between (struct vclprog).warm that is used as a
boolean, unlike the second parameter of mgt_vcl_setstate. We don't use
an actual C enum but const char[] to make debugging easier.

	import vmod from "/some/dir/"

and have the default vmod shlib filename appended.

know the filename of the -f argument, it should be possible to
include "./" relative to it.

The footnote is that the include is resolved at lower privlevel
than the -f file is read, so in really obscure cases you could
have really obscure error messages.

VCL file, and illegal everywhere else.

This makes it easier to distribute "VCL-packages"

Test-case written by:	Kacper

the VCL fileopening logic in mgt so we have it only one place.

away const.

all other methods use rdlock

for more clarity, before we start hacking VCC further.

Submitted by:	github::onovy