Integrating EXSLT and cleanup:

Integrating EXSLT and cleanup:
* Makefile.am configure.in libexslt/Makefile.am:
  Integration of libexslt in the build system
* libxslt/Makefile.am libxslt/xsltproc.c libxslt/xsltutils.c
  xsltproc/Makefile.am xsltproc/xsltproc.c:
  Moved xsltproc to a separate directory, linked it to libexslt,
  and added exslt version reports to -V
* tests/*/Makefile.am: updated the path to xsltproc
* libexslt/common.c libexslt/exslt.h libexslt/exsltconfig.h.in
  libexslt/functions.c libexslt/math.c libexslt/sets.c: added
  versionning informations, some cleanup, and added documentation
  to a couple of exported functions
Daniel