Merged all the namespace lookup/create/disable functions into

Merged all the namespace lookup/create/disable functions into

* libxslt/attributes.c libxslt/attrvt.c libxslt/namespaces.c
  libxslt/namespaces.h libxslt/preproc.c libxslt/templates.c
  libxslt/transform.c libxslt/variables.c libxslt/xslt.c
  libxslt/xsltInternals.h libxslt/xsltutils.c:
  Merged all the namespace lookup/create/disable functions
  into xsltGetSpecialNamespace(). Changed xsltGetNamespace()
  and xsltGetPlainNamespace() to call xsltGetSpecialNamespace(),
  but kept the ns-aliasing mechanism; the ns-aliasing needs
  to be removed when we move to the refactored code, which
  applies ns-alias only at compilaton time.
  Refactored xsltElementComp() (preproc.c); enhanced error reports.
  Fixed: if the "namespace" attribute was not given, then this
  performed incorrectly only a lookup for a default namespace;
  i.e., without taking any prefix on the "name" attribute into
  account.
  Refactored xsltElement() (transform.c); enhanced error reports.
  Refactored xsltAttributeComp() (preproc.c). Added namespace
  lookup as in xsltElementComp(). Enhanced error reports.
  Refactored xsltAttribute() (transform.c); enhanced error reports.
  xsltCopyTreeInternal(): eliminated the need to call xmlGetNsList()
  for every element in the tree; this needs to be done only for
  the top-most elements. For subsequent elements reconcile only
  the ns-declarations. Disallowed setting of ns-declarations if
  children have been already added to an element.
  Removed ns-aliasing code where necessary.
  xsltCopyProp(): disallowed setting of attribute nodes if
  children have been already added to an element.
  xsltCopy(): removed the incorrect skipping of attributes in the
  XSLT namespace. Removed the incorrect ns-aliasing for attributes.
  Changed to use the introduced function xsltShallowCopyAttr().
  xsltShallowCopyAttr():  Centralized all attribute-copy related
  code in this function. It will now be called by
  xsltCopyTreeInternal(), xsltCopyOf() and xsltCopy().
  xsltCopyAttrListNoOverwrite(): Renamed. Refactored. Optimized to
  use xsltGetSpecialNamespace() and xmlNewDocProp().
  Further substitution of various scattered namespace-lookup
  related code for the use of xsltGetSpecialNamespace().
  xsltAttrTemplateProcess(): Refactored. Removed the incorrect
  processing of attribute-sets. Attribute sets need to be applied
  before adding any normal attribute of the literal result element;
  this is now done in  xsltAttrListTemplateProcess(). Fixed to
  ensure that the ns-prefix of the overwriting attribute is used.
  xsltAttrListTemplateProcess(): Refactored. Moved semantics from
  xsltAttrTemplateProcess() over to this function in order to
  optimize processing of multiple attributes. This does not call
  xsltAttrTemplateProcess() anymore.
  Fixed: do not exclude the XSLT namespace after ns-aliasing have
  beed applied.
  The IFDEFed-out refactored code fixes the following issues:
  - #313711: namespace collision with namespace-alias (reported
              by by Oleg Paraschenko)
  - #338214: Incorrect scope for exclude-result-prefixes
  - #341392: Excluding namespace declarations of literal result
             elements.
  - #341325: Namespace aliasing and resulting namespace prefixes
  Already enabled fixes:
  - #344183: xsl:copy misses to copy attributes in the XSLT namespace
  - #341463: Namespace-alias using #default for result-prefix with no
  	     default namespace in scope
  - #313890: namespace collision with xsl:element and xsl:attribute,
  	     reported by Oleg Paraschenko
  - #344176: xsl:copy misses to set an element's namespace-URI in
             some cases
  - #305739: the "name" QName of xsl:element is incorrectly always
  	     resolved to the default namespace