refactored appending a bit. addable() now tests illegal reconnection of parents.


git-svn-id: https://ilk.uvt.nl/svn/sources/libfolia/trunk@16456 12f355fe-0486-481a-ad91-c297ab22b4e3
eeeeek


git-svn-id: https://ilk.uvt.nl/svn/sources/libfolia/trunk@16458 12f355fe-0486-481a-ad91-c297ab22b4e3