Eliminate libvarnish.h embedded #includes.

We now have
	<vapi/vs[mcl].h> for the programmatic API

	<vapi/vs[cl]_int.h> for the underlying structure,
			    shared between API and varnishd

the tbl/ subdirectory

This is based on output from some scripts and basic sanity testing.

and external files are included with <...>

crashing child to do so, and then explicitly start it again.

avoid fixed sleeps waiting for the child process to start.

Fixes: #1024

1 thread is a bit on the low side, make the default on RPM based
distros 50.

Please let me know if any of them are way off