Add portable dev/sort-z; link into t/bin/; use in test-meta.sh

Add portable dev/sort-z; link into t/bin/; use in test-meta.sh

Add a dev/sort-z wrapper to handle sorting null terminated lines
across platforms.  Apparently NetBSD supports "-R 000" instead of -z.

Add a t/bin for any commands we want to make available to all tests,
symlink sort-z there, and add it to the PATH in test-meta.sh.

Thanks to Greg Troxel for reporting the problem.

Signed-off-by: Rob Browning <rlb@defaultvalue.org>