Refer to the 'kyua' package in FreeBSD/NetBSD

The pkgsrc and ports systems have been updated to 0.10, so they now
only provide a 'kyua' package instead of 'kyua-cli'.  Document this
and tell users to install 'kyua' directly.

The Fedora package for 'kyua' has been submitted for review but it is
not ready yet for being replaced here.