Althought libxml2 is thread safe and libxslt is not very thread sensitive, they both suffer
some problems if used ``from modules'' by web servers like apache or apache2 (take a look
to the thread on the libxml and libxslt mailing lists).
mod-xslt tries to lessen the impact of libxml/libxslt lack of support for modularized
environments by trying to use some libxml2 internal functions.
The message just warns you that some compatibility layers have been enabled since some
of the needed functions were missing. If you want to get rid of the warning, please patch
the library (read README-Patches.sgml). Most of the times, you can just ignore this message
since the ``compatibility layer'' will take care of everything.