(vertical_scroll_bar_type): Add enumerated

(vertical_scroll_bar_type): Add enumerated
none/left/right type for identifying vertical scroll bars.
(struct frame): Use vertical_scroll_bar_type.
(FRAME_HAS_VERTICAL_SCROLL_BARS): Use vertical scroll bar type.
(FRAME_VERTICAL_SCROLL_BAR_TYPE): New macro.
(FRAME_HAS_VERTICAL_SCROLL_BARS_ON_LEFT): New macros.
(FRAME_HAS_VERTICAL_SCROLL_BARS_ON_RIGHT): New macros.
(FRAME_SCROLL_BAR_WIDTH, FRAME_LEFT_SCROLL_BAR_WIDTH): New macros.
(FRAME_WINDOW_WIDTH, FRAME_WINDOW_WIDTH_ARG): New macros.
(SET_FRAME_WIDTH): New macro.
(WINDOW_VERTICAL_SCROLL_BAR_COLUMN): Modify to handle left-side
croll bars too.