(at leat on solaris) strerror() itself may fail for an out-of-memory
condition (because the localization code contains memory
allocations). In order to handle this situation, we need to save the
original errno because strerror() may also set errno.

Fixes #2815

This reverts commit ee33662a.

This may reduce our binary size.

seen by sun cc as:

"cache/cache_vrt_priv.c", line 54: syntax error:  empty declaration (E_EMPTY_DECLARATION)
"cache/cache_vrt_priv.c", line 109: syntax error:  empty declaration (E_EMPTY_DECLARATION)

The vcl and id members served no purpose except for debugging.

With this, we save 2 * sizeof(uintptr_t), which is exactly the
additional footprint introduced with red/black trees. So the
net footprint of a struct vrt_priv is now back to what it had
been before #2813.

For debugging, it should also be trivial to induce the context
from the address of the tree root.

O(n) does not scale for a high number of dynamic privs, so trade some
workspace for O(lg n)

Ref: #2812

sed 's:VRB_:VRBT_:g' -i "$FILES_CHANGED[@]"

Closes #2812

Fixes #2820

Enabled when using varnishtest -L.

(at leat on solaris) strerror() itself may fail for an out-of-memory
condition (because the localization code contains memory
allocations). In order to handle this situation, we need to save the
original errno because strerror() may also set errno.

This issue exists in many more places all over the code, but in the
pool_breed case we likely failed pthread_create for an out-of-memory
condition, and in the panic handler we want to make sure that we
trip no follow-up panic under any circumstances.

In general, while fixing all strerror() calls would unnecessarily
complicate the code, doing so should be justified for these cases.

Fixes #2815

the priv id is basically equivalent to the head (struct vrt_privs),
and a vrt privs list thus can not contain privs with another id.

So we could also retire the id member of struct vrt_priv...

we could also retire the vcl member of struct vrt_priv, but it could
be useful for debugging.

completely irrelevant historical note:

IIUC, ~20+ years ago, "slowlaris" was referring to Solaris being
percieved as "much slower than linux" (which was partly true, but
also related to the fact that linux had less mp support at the time)

Tests #2809

Fixes: 	#2809

Always make "* top %f TEST ${test} starting" the first message.

Tag vtest and varnishtest message with "VTEST" instead of "TEST"

The vmod name got lost in e7c04974

example before/after diff:

- new xshard_param = shard_param()
+ new xshard_param = directors.shard_param()

... after feedback from @slimhazard aka Geoff