Fringe cleanup.

Fringe cleanup.
Comment fixes. Use renamed symbols.
(fringes_extra): Renamed from flags_areas_extra.
(FRAME_FRINGE_BITMAP_WIDTH): Renamed from FRAME_FLAGS_BITMAP_WIDTH.
(FRAME_FRINGE_BITMAP_HEIGHT): Renamed from FRAME_FLAGS_BITMAP_HEIGHT.
(FRAME_X_FRINGE_COLS): Renamed from FRAME_X_FLAGS_AREA_COLS.
(FRAME_X_FRINGE_WIDTH): Renamed from FRAME_X_FLAGS_AREA_WIDTH.
(FRAME_X_LEFT_FRINGE_WIDTH): Renamed from FRAME_X_LEFT_FLAGS_AREA_WIDTH.
(FRAME_X_RIGHT_FRINGE_WIDTH): Renamed from
FRAME_X_RIGHT_FLAGS_AREA_WIDTH.