The VMOD_DIR returned from pkg-config does not take prefix and similar
variables into account. Make sure to pass an explicit VMOD_DIR that
the build process has write access to.

Fixes #8

Exit with an error if we can't find libvarnishapi, instead of
just warning about missing macros.

This is useful for changing all references of libvmod-example/example
into your new vmod name.

One-off task for all vmods, but if you write more than a couple you
quickly get fed up with this drudgery.

Conflicts:
	configure.ac

Make man page generation generic