mc6845: Added display enable and horizontal/vertical back porch widths to the update function. Updated some MESS drivers to make use of this. [Curt Coder]

(MESS) pet: Added the "Fat 40" PET/CBM 4032 models. Check out "No Pets Allowed" by Orb to see them and the new mc6845 functionality in action. [Curt Coder]