Scroll selected window display ARG columns right.
Default for ARG is window width minus 2.
Value is the total amount of leftward horizontal scrolling in
effect after the change.
If SET-MINIMUM is non-nil, the new scroll amount becomes the
lower bound for automatic scrolling, i.e. automatic scrolling
will not scroll a window to a column less than the value returned
by this function. This happens in an interactive call.
(fn &optional ARG SET-MINIMUM)