fix the processing of top level elements of stylesheets which are not in

* libxslt/xslt.c libxslt/extensions.c libxslt/extensions.h:
  fix the processing of top level elements of stylesheets which
  are not in the XSLT namespace and are not an extension either
  should fix #529223
* tests/docs/Makefile.am tests/docs/bug-167.xml
  tests/general/Makefile.am tests/general/bug-167.*: add the
  test to the regression suite
Daniel

svn path=/trunk/; revision=1472