Fixed SGML catalogs breakage of 2.4.7, added a couple of really needed

* include/libxml/catalog.h catalog.c: Fixed SGML catalogs
  breakage of 2.4.7, added a couple of really needed APIs
  like xmlCatalogIsEmpty() and xmlNewCatalog()
* xmlcatalog.c: updated --sgml --noout to be a suitable replacement
  for install-catalog
* configure.in: preparing 2.4.8
Daniel
6 files changed