Log Message:
varnish: update to 6.6.0

Based on pkgsrc-wip 5.1.1 package by Filip Hajny.

Changes in Varnish 6.0
  Support for UDS (Unix Domain Sockets)
  Because UNIX Domain Sockets have nothing like IP numbers, we were forced to
  define a new level of the VCL language vcl 4.1 to cope with UDS.
  The HTTP/2 code has received a lot of attention from Dag Haavi Finstad
  (Varnish Software) and it holds up in production on several large sites now.
  There are new and improved VMODs:
    vmod_directors – Much work on the shard director
    vmod_proxy – Proxy protocol information
    vmod_unix – Unix Domain Socket information
    vmod_vtc – Utility functions for writing varnishtest cases.
  The umem stevedore has been brought back on Solaris and it is the default
  storage method there now.
  More error situations now get vcl failure handling, this should make life
  simpler for everybody we hope.
  And it goes without saying that we have fixed a lot of bugs too.

Changes in Varnish 5.0
  Varnish 5.0 changes some (mostly) internal APIs and adds some major new
  features over Varnish 4.1.
  Separate VCL files and VCL labels
  Very Experimental HTTP/2 support
  The Shard Director
  Hit-For-Pass is now actually Hit-For-Miss
  Ban Lurker Improvements
  Request Body sent always / "cacheable POST"
  ESI and Backend Request Coalescing ("waitinglist") Improvement
  Backend PROXY protocol requests
  Default VCL search path
  devicedetect.vcl
  varnishtest
  misc
  News for VMOD authors

Changes in Varnish 4
  Varnish 4 is quite an extensive update to Varnish 3, with some very big
  improvements to central parts of varnish.
  Client/backend split