Port t_db.sh to FreeBSD

- The blocksize on FreeBSD is 32kB, not 64kB
- Add some detection for MK_DICT == no; /nonexistent is echoed along with
  atf_skip to ensure that the test will fail if dict(..) is called in the
  non-final stage of the pipeline

Submitted by: pho


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274061 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
inet_network on FreeBSD returns NULL when provided "0x" to inet_network

Submitted by: pho


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274062 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f