This reverts commit 0f90ee22.

After looking at this again, I see that the busyobj is cleared as it
should as part of VBO_DerefBusyObj(). Reverting the patch.

- use -fstack-protector only if both compiler and linker support it
- use -Wno-missing-field-initializers vs -Wno-extra depending on compiler support
- -Wno-pointer-sign only if compiler supports it
- add -Wno-address to avoid "the address of ‘buf’ will never be NULL" warning in
  cache_backend_cfg.c (and in other places where REPLACE() is used with local
  buf variable)

Fixes: #1458

Move the vmod man pages to man/ and build and ship the vmod_director
page.  Also make sure we use the vmod_std docs from the .vcc file, not
the old copy in docs/

Don't use {} in one-liners

To help track our adoption rate of the new Varnish versions, add the major
version in the default Via header added by us.

It makes sense to default to setting Connection: close for vcl_pipe.
Do this before calling vcl_pipe so it's overrideable.

Fixes #1455

Remove adding of X-Forwarded-For from builtin.vcl and put it into the
C code that runs before vcl_recv.  This makes it more likely that it's
properly set when the user VCL runs.

Fixes: #1454

Mostly an attempt at pointing people that send pull requests on Github
in the right direction.

Move showing of debug counters from 'h' key to 'd' inside a running
varnishstat.