Add new function tokenizer(), usable from XSLT
Add new function tokenizer(), usable from XSLT

tokenizer() is not very interesting yet, when sdsc eventually gets
a real tokenizer, though, it should help that everywhere we need
to tokenize, the same function is used already.
More immediately, we can now use the tokenizer from XSLT which helps
to improve the error underlining feature

sknorr/suse-doc-style-checker,sknorr/suse-doc-style-checker,sknorr/suse-doc-style-checker