Unit tests for matrix.h. Specifically translate routines.

Change-Id: Id6fe1187ff3e97d459e5b97254a75b04d18e377b
Reviewed-on: http://www.matthewh.me/gerrit/8
Reviewed-by: Matthew Hoggan <matthew.hoggan@matthewh.me>
Tested-by: Matthew Hoggan <matthew.hoggan@matthewh.me>