xsl:element generated superfluous xmlns declarations, closes bug #99905

* libxslt/transform.c: xsl:element generated superfluous xmlns
  declarations, closes bug #99905
* tests/docs/Makefile.am tests/docs/bug-101.xml
  tests/general/Makefile.am tests/general/bug-101.*: added the
  example in the regression tests for this case
Daniel