This fixes 2 inaccuracies in the recently added SQL99 feature list docs.

This fixes 2 inaccuracies in the recently added SQL99 feature list docs.
UNIQUE and DISTINCT predicates are both listed as implemented -- AFAIK,
neither is.

I also included another trivial patch which adds the default location
of the DSSSL stylesheets on my system (Debian unstable, docbook-dsssl
1.76) to the list of paths that configure looks for.

Neil Conway