* Improve the accuracy of line numbers for text nodes, so that reported errors about syntax or evaluation errors in expressions point to the right line (not quite perfect yet, though). * Evaluation errors in expressions now include the original expression code in the traceback.

This example shows how to transform some HTML input, while adding
elements such as headers, and using <em>/<strong> instead of <i>/<b>.
The output is that a proper XTHML document.