- Clear deprecated flags for ID's: Scene, Sequence, World, Object & Mesh. - Clear deprecated flags for Spaces: outliner, 3D view & image. - Remove unused `Mesh.drawflag` - Remove unused `USER_ALLWINCODECS`, `USER_MMB_PASTE`. - Remove `V3D_SOLID_TEX` & `V3D_ZBUF_SELECT` - used in a few areas. - Flip `Object.empty_image_visibility_flag` (avoids do-version on each new flag) - Rename 'Backside' -> 'Back' in context of drawing - showing 'Back' makes sense.