I work with NetBeans, and it insists on this being present.

if sub is null (because it's the contents of a non-existing header),
pretend it's "" instead.

Add a link to the varnishlog man page and the logging chapter in the tutorial

remove -i and -I, add -m and describe it. Simplify the docs. The user only needs to care about -m, really

I'm not sure if we should go into more detail about how the whole thing works

Fixes #1062

of maintaining magic hex-bit values that must match.

Fixes #1042