[bugfix] eXist 2.0 depends on Servlet API 3.0
Change makes code consistent. Patch by Christian Mahnke
Merge pull request #20 from wolfgangmm/develop

XQuery optimizer fails on several types of expressions
Merge pull request #21 from dizzzz/feature/tomcat6-fix

[bugfix] eXist 2.0 depends on Servlet API 3.0