The only real usage was in the frontend to generate a .xkm file. The
rest of the code just operated on the attached XkbDescPtr. Note that
here we've replaced the usage of the defined field in CompileKeymap with
the equivalent field in a XkbcDescPtr.
A copy of the xkbcomp sources (except the frontend) have been copied in
to provide a means to compile a XkbDescPtr. This definitely doesn't
build or do the right thing yet.