Document current vcl_backend_* situation.
Remove references to libvmod-example.
Update to libvmod-example standard.
Pull in some sweetness from libvmod-example.
Add /usr/sbin to path when looking for varnishd.
Require recent autoconf.

On EL6 systems the packaged 2.63 version is missing AS_VAR_COPY.
This seems to have been added in 2.63b, released sometime in 2008.

With this commit we cut off any vmod development being done on
EL6 and earlier. (building and running should work)

Conflicts:
	configure.ac
Use version from variable/automake.
Confusing RPM variables leads to hard coding.
That experiment did not work out. Hack it.
My head hurts.
Update to libvmod-example standard.