(x_bitmap_icon, x_make_frame_visible): Remove declarations.

(x_bitmap_icon, x_make_frame_visible): Remove declarations.
(XSetFont): Add declaration.
(mac_set_forecolor, mac_set_backcolor, mac_set_colors): Remove
functions.
(GC_FORE_COLOR, GC_BACK_COLOR, GC_FONT, MAC_WINDOW_NORMAL_GC): New
defines.
(XDrawLine, mac_draw_line_to_pixmap, XClearWindow)
(mac_draw_bitmap, XCreatePixmapFromBitmapData, XFillRectangle)
(mac_draw_rectangle, mac_draw_string_common, mac_scroll_area): Use
them.
(mac_erase_rectangle): New function.
(XClearArea, x_draw_fringe_bitmap, x_clear_glyph_string_rect)
(x_draw_stretch_glyph_string): Use it.
(XChangeGC, XCreateGC, XGetGCValues, XSetForeground)
(XSetBackground, XSetFont): Adjust for new GC implementation.
(x_draw_fringe_bitmap, x_draw_box_rect): Use GC to set colors.
(XTset_vertical_scroll_bar): Clear area under scroll bar.