* libxslt/extensions.[ch] libxslt/functions.[ch] libxslt/preproc.c
	  libxslt/transform.[ch] libxslt/variables.c libxslt/xslt.c
	  libxslt/xsltInternals.h: new extension framework.
	  Added stylesheet module data, top-level and extension elements
	  precomputing, global registration of top-level elements and
	  extension elements and functions.
	  Extensions are no longer initialized from extension-element-prefixes
	  declarations but when modules need the data.
	  init/shutdown functions registered with xsltRegisterExtModule{,Full}
	  only allocate and free module data, they shouldn't register the
	  elements and functions any more.
	* libxslt/xsltutils.c: fixed a bug in xsltPrintErrorContext when
	  @node wasn't NULL.
	* libxslt/xslt.c: fixed xsltPrecomputeStylesheetTop which allowed
	  non-XSLT top-level elements before any xsl:import element.
	* libexslt/common.c libexslt/functions.c libexslt/math.c
	  libexslt/sets.c: adapted to use the new extension framework.
	* libxslt/functions.c libxslt/extensions[ch] xsltproc/xsltproc.c:
	  moved the test module from functions.c to extensions.[ch],
	  modified it to use the new extension framework. Updated xsltproc
	  to register the test module.