At present mostly consisting of XXX's.

Fixes #2416

Closes #2421

To be revisited post release.

References #2421

Refs da91fec9

decode() and transcode() now have an optional parameter length;
if length > 0, decode that many characters from the encoded string.

References #2421

This is mostly a mechanical patch.

For HEX and URL, there is now an ENUM case in {LOWER, UPPER} to
determine the case of hex digits produced for an encoding, default
LOWER.

Spotted by:	fgs

If the cli buffer is allocated on the stack, the mgt process will
crash hard for big values of this parameter. Instead we allocate on
the heap.

The new cli buffer an "auto" VSB. This means that the varnish
parameter cli_buffer is ignored from now on, and the manual marks it
as deprecated.

Closes: #2382

Don't attempt to free the static empty string that the VMOD assigns
for empty encodings.

blob objects.

Revealed by GCOV.

Works for all, check, install targets but not for individual targets,
see ref: https://www.gnu.org/software/automake/manual/html_node/Built-Sources-Example.html

Fixes #2423

The goal of `req.ttl` is to allow lower requirements for known
transactions (since this has to be done in VCL) but objects with
an age higher than `req.ttl` would always be considered expired
during lookup even if their actual TTL (obj.ttl) is still positive.

Ignoring `req.ttl` gives a better control over explicit refreshes
made to optimize latency and greatly reduces the risk of running
into #1799 (for a subset of use cases).

Closes #2422

$Event RST test again.

There are undoubtedly better ways, but I couldn't find them...

It's no longer used anyway, and was already called via the generic
VUT_Arg function.

We don't need an indirection in a separate C file per VUT.