Fix template rules which use a variable reference in the value of the match
attribute. This is not allowed according to "5.3 Defining Template Rules"
in REC-xslt-19991116, XSL Transformations (XSLT) Version 1.0.
The xsltproc utility prior to version 1.1.15 allowed this erroneously
but in the latest version it has been fixed.

Reported by: scottl