* Enforced stripping of whitespace in some XSLT elements (e.g. xsl:choose) to
  relax Libxslt's content checks.
  Stricter checking for elements with an empty content: only whitespace 
  is allowed.
  This follows the observations and suggestions in:
  http://mail.gnome.org/archives/xslt/2006-May/msg00044.html

* IFDEFed (XSLT_REFACTORED_XSLT_NSCOMP) experimental code which allows for
  pointer-comparison of the XSLT namespace name (elem->ns->href).

* Introduction of an info-struct for literal result elements. Those will
  be created on demand; i.e., only when the set of effective namespace
  declarations has changed, there will be created a new info-struct and
  shared by similar literal result elements. 
  * Computation of the effective namespace declarations of literal result
    elements at compile-time.
    - Introduced xsltEffectiveNs
  * Namespace Aliasing:
    - Introduced xsltNsAlias
    - Computed and applied now at compile-time
    - This modifies the set of effective namespace declarations of
      literal result elements
    - node->ns entries are remapped to the target ns-declarations
    - node->properties->ns are remapped to the target ns-declarations
    In order to avoid addition of ns-decls to the tree, new ns-decls needed
     for the ns-aliasing are stored in xmlDoc->oldNs; note that this means
     that the tree eventually won't be namespace wellformed anymore
     after compilation.
    Thus we don't need anymore any ns-aliasing code at transformation-time
     (removed all ns-aliasing code from namespaces.c).
    The prefix of the ns-declaration in-scope for @result-prefix will
     be user rather than the prefix specified in @stylesheet-prefix.
  * In-scope namespaces are stored in the info-struct; thus we'll be able
     in the future to use those for execution of XPath expressions (rather
     than the currently used namespace hash, which needed distinct ns-prefixes
     in the tree; this restriction will be eliminated in the near future).

* Applied the suggestion of Jerome Pesenti: The XPath
  compilation context (accessible via the compilation context)
  is now reused for compilation of expressions at compilation-time;
  this should reduce compilation time to 50% for avarage stylesheets.

* Initial rewrite of the sequence-constructor ("template") processing
  code during transformation; i.e., the instantiation of the "template".

* Added commencts here & there