Clamp vsl_space and vsm_space to 4GB
Clamp vsl_space and vsm_space to 4GB

Fixes: #1750

gquintard/Varnish-Cache,gquintard/Varnish-Cache,feld/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache,gquintard/Varnish-Cache,feld/Varnish-Cache,feld/Varnish-Cache,feld/Varnish-Cache