git-svn-id: https://free-cad.svn.sourceforge.net/svnroot/free-cad/trunk@5140 e8eeb9e2-ec13-0410-a4a9-efa5cf37419d
+ detect well known invalid values for setDatum + hide some negative distance datums in the gui git-svn-id: https://free-cad.svn.sourceforge.net/svnroot/free-cad/trunk@5133 e8eeb9e2-ec13-0410-a4a9-efa5cf37419d
git-svn-id: https://free-cad.svn.sourceforge.net/svnroot/free-cad/trunk@5000 e8eeb9e2-ec13-0410-a4a9-efa5cf37419d