upgrading to v4, change of "req.backend.healthy" -> "std.healthy(req.backend)" reports "Symbol not found: 'std.healthy' (expected type BOOL)"

[grantksupport at operamail.com]

> Ok then, what's the output of the following command?
> 
> sudo varnishadm param.show vmod_dir

sudo varnishadm param.show vmod_dir
	Not a VSM file /usr/local/var/varnish/SITE/_.vsm

ls -al /usr/local/var/varnish/SITE/*.vsm
	-rw-r--r-- 1 root root 81M May  4 08:19
	/usr/local/var/varnish/SITE/_.vsm

file /usr/local/var/varnish/SITE/_.vsm
	/usr/local/var/varnish/SITE/_.vsm: data