cgd devices in XEN* configs

["Johnny C. Lam" <jlam%pkgsrc.org@localhost>]

The i386 and amd64 GENERIC kernels have been modified to include the cgd 
pseudo-devices by default.  I think the XEN* kernels should match this 
change so that the XEN* kernels can be drop-in replacements for users of 
GENERIC kernels.  Would this change be alright to make?

        Thanks,

        -- Johnny C. Lam