An additional keys test

Still may need to adjust this a little more: there seems to be an additional
error message at present. As the input is wrong, that is not so bad but should
get fixed.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4535 de43f980-851b-0410-b2f7-c40aca1f87e0
Two arguments reversed in an error message


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4536 de43f980-851b-0410-b2f7-c40aca1f87e0
Abort key definition if property is not given

The older version gave two error messages, the first correct and the second
looking for a random property. This check-in uses a special 'property' name
to avoid this.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4537 de43f980-851b-0410-b2f7-c40aca1f87e0