Note that each VMOD only gets one of each, so that the same 'vmod_priv'
will appear on all VMOD functions which use PRIV_REQ and similarly
only a single vmod_priv appear for all PRIV_SESS uses in that VMOD.

Feedback welcome.

gets too complicated.

This is all Slink's fault.

For quoted tokens, http_GetHdrToken should not try a case insensitive match
if the sensitive match fails

implementation

If the type of the y argument to RDN2/RUP2 is smaller than the type of
the x argument, these macros would fail to round correctly. Cast to
uintmax_t to avoid this problem.

fails too.

director layer.

implementation bits.  Still not there, but getting closer...

Now bereq.backend is the backend or director we chose, whereas
beresp.backend is the actual backend, after directors have done their
picking and choosing, which sent us the reply.

Constify the VCL_BACKEND datatype.

This is called recursively until we get to the bottom of the pile.

Doing it this way means that "pick one" directors dont need to know
about other methods on directors and can concentrate on just picking.

It also prevents us from eating up a lot of stack.

Round up vary length to make sure that the object workspace can take
the rounded up Vary string without overflowing.

backends.

(VDD14q3 item)

(VDD14q3 item)

Fixes #1598

linebreaks in panic messages.