GitLab

Delete last vestige of fieldlist slot.
(Fregion_fields): Finally deleted.

(overlays_at, recenter_overlay_lists): New functions.
(Fmake_overlay, Fdelete_overlay, Foverlay_get, Foverlay_put): Likewise.
(Fmove_overlay, Foverlays_at, Fnext_overlay_change): Likewise.
(Foverlay_lists, Foverlay_recenter): Likewise.