Replace Xalan's XPath with the JDK version

[carlosame]

This project uses a Xalan fork called EchoXSL, however it still depends on code from the Apache Xalan project (unlike EchoSVG, EchoXSL keeps the org.apache packages and only uses code from the Apache Xalan repositories).

Due to concerns about the Xalan project (as well as the BCEL project that it depends on), I decided to use the JDK's XPath support instead of the Xalan fork, porting a commit from Apache Batik.

I'm not convinced that the Batik patch is 100% backwards compatible with what Xalan did, but one cannot really count on the future of Xalan. And I'm not willing to work on improving Xalan as I did with Batik: XPath and XSL(T) are dead technologies (modern web technologies use CSS selectors instead of XPath).