libxslt/transform.c libxslt/functions.c: Added the extension API
  suggested by Thomas Broyer, this should allow implementation of
  EXSLT for example.
- libxslt/extra.[ch]: added a fake xsltFunctionLocalTime() in Norm's
  CVS extension namespace to avoid complaints, some cleanup
- configure.in tests/Makefile.am tests/extensions/*: added a test
  for new modules testing both elements and functions registration
Daniel