preparing 1.1.13, updated and rebuilt the docs. trying to fix some build

* NEWS configure.in doc/*: preparing 1.1.13, updated and rebuilt
  the docs.
* tests/plugins/Makefile.am xsltproc/Makefile.am: trying to fix
  some build problems.
* libxslt.spec.in: adding a build require and a require for
  libgcrypt-devel, c.f. Red Hat bug #133211
* libxslt/xsltInternals.h: as for libxml2, XML_CAST_FPTR was wrong.
Daniel