It is very easy to confuse the child process' vcl_active and the
management process' active_vcl variables.

Rename mgt's active_vcl to mgt_vcl_active, following the naming scheme
used elsewhere.

Add a ASSERT_VCL_ACTIVE() macro that asserts that vcl_active either is
NULL or points to a VCL that is warm.

Sprinkle this macro in the various calls throughout the child process that
are involved in VCL handling.

Patch by: @alveelde

Do not select the first VCL present as the active VCL in the child
process. Instead it should always use what the mgt process tells it
through the explicit 'vcl.use' commands it will send.

Previously, the child could select a cold VCL as the active VCL if that
happened to be the first one present to it during restarts. This could
lead to asserts as that is not an allowed state.

Using the wrong list variable would cause the dependency check to consider
VCLs that were not attempted discarded.

Fixes: #3734

For the REGEX type, we now peek ahead after the first CSTR token if a '+'
operator follows and, if yes, create the pattern as a concatenation.

Fixes #3726

Conflicts:
	bin/varnishtest/tests/v00022.vtc

As a follow-up issue from #3719, it was noticed that dynamic calls to
built-in SUBs did not work.

This issue was caused by more (struct symbol) members missing
initialization in VCC_New().

In turn, it became apparent that the evaluation context check in
vcc_expr5() as tested in v00020.vtc only worked by accident, and only
for built-in subs because (struct symbol).eval was NULL for built-in
subs.

We fix SUB type expression evaluation with a type specific evaluation
function which allows expression evaluation from explicit SUB contexts
only.

Fixes #3720

vcc_act_call() implements use-before-define semantics. To do so, it
needs to instantiate SUB symbols if they do not exist.

However, it wrongly called VCC_GlobalSymbol() also for existing
symbols, overwriting symbol properties.

In the case of the built-in subs, the symbol's lname (historically)
still is the unescaped literal name, while user defined subs have
their name escaped via VCC_GlobalSymbol() -> VCC_PrintCName().

This made the wrong call to VCC_GlobalSymbol() apparent when a
built-in sub was called with an explicit "call" action.

Besides fixing the VCC_GlobalSymbol() call, we also need to set the
lname and rname attributes for built-in SUB symbols initialized in
VCC_New().

Alternatively, we could also have used VCC_GlobalSymbol() there, but
that would have affected other places where we (still) rely on the
known name scheme of built-in subs, e.h. EmitStruct(). While the name
unifaction was nice in general, I found the necessary changes (look up
SUB symbols) not worth the benefit.

Fixes #3719

Fixes #3706

The CircleCI default commit behaviour is changed to package building now
that this is a release branch.

Refs 33ffbbc5

Refs 33ffbbc5

Or when the -p option is used.

Fixes #3687

and sort options alphabetically while being at it.

Relates to ##3687

Spotted by @Algunenano.

To avoid mixing vmod_std coverage with the VMOD feature.

With a tiny bit of polish here and there.

I'm purposefully leaving the shard direcor and vmod_std alone for now.

The previous ones were antiquated.

And bionic inherits the "oldest Ubuntu" 32bit setting.

The variable is independent of req.esi / resp.do_esi:

Whether or not the backend side prepares an object for ESI has nothing
to do with whether or not the client side processes it.

To avoid the maintenance of a downstream patch.