Fix meinproc's inability to handle source/build/install paths with spaces correctly. This is fixed by using XML catalog files instead of SGML catalog files because XML catalog files can be specified via URLs while SGML catalog files can only be specified as paths without the possibility to properly escape spaces.

Detailed description of the changes:
- Replace all "catalog" files under kdoctools/customization by "catalog.xml" files.
- Add docbook/xml-dtd-4.1.2/catalog.xml (XML version of docbook.cat).

CMakeLists.txt
- Install the "catalog.xml" files instead of the (removed) "catalog" files.

meinproc.cpp
- Make xmllint use the XML catalog files instead of the SGML catalog files. This fixes syntax checking for paths containing spaces.

xslt.cpp
- Set XML_CATALOG_FILES and call xmlInitializeCatalog() which uses the XML catalog files specified by XML_CATALOG_FILES. xmlLoadCatalogs() cannot be used because it expects a space- and/or colon-separated list of file path.

Should eventually be ported to branches/KDE/4.0.