add test for cookie field constants


git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@36142 72102866-910b-0410-8b05-ffd578937521
add a couple of substitution tests


git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@36143 72102866-910b-0410-8b05-ffd578937521