(XTset_vertical_scroll_bar): Block input when clearing

(XTset_vertical_scroll_bar): Block input when clearing
under newly created scroll bar.
(expose_window): If window is not yet fully initialized, do
nothing.  This can happen when toolkit scroll bars are used and a
window is split.  Reconfiguring the scroll bars will generate an
expose for a newly created window.
(x_alloc_nearest_color_for_widget) [USE_X_TOOLKIT]:
New.  Allocate color for lwlib widgets.
(x_alloc_nearest_color): Change parameter list include the
frame on which to allocate colors.  Gamma-correct colors.
(x_alloc_lighter_color): Call x_alloc_lighter_color with new
parameter list.