Add cscope support
Add a -N option for use with utilities. This takes a VSM filename as argument, and will also disable the abandonment checks.

This allows reading a stale VSM file (e.g. _VSM.keep saved from a
panic) for forensics gathering.
Add test for multiple Host headers
Finally pull the remains of cnt_fetch() entirely into VBF_Fetch()
Instigate a bit of VTLAism on the Varnish Backend Fetch code
Nail down the asserts where we want them.
One comment and N > 0 bugs from goal...
Register the busyobj on the thread while we do fetch-thread duty.
Write the request body to the right wrk's wrw
Oops, that bit was still two test-cases to early