Revert previous change to styled converter and modify the test code instead.

Now create a new converter for each operation. I don't think calling end() more
than once is a good idea even if it can be made to work.

git-svn-id: http://svn.mkgmap.org.uk/mkgmap/trunk@2788 25d90789-57f7-4ee0-8453-03a3dfeeeb22