added check for memory allocation error (bug #400242); fixed "type-punned

* libxslt/pattern.c: added check for memory allocation error (bug #400242);
  fixed "type-punned pointer" warnings.
* libxslt/xsltutils.c: added checks for memory allocation error
  (bug #400242)
* restored NEWS, doc/EXSLT/downloads.html which mysteriously disappeared
  from svn

svn path=/trunk/; revision=1419