Set the fringe widths of window WINDOW.
WINDOW must be a live window and defaults to the selected one.
Second arg LEFT-WIDTH specifies the number of pixels to reserve for
the left fringe. Optional third arg RIGHT-WIDTH specifies the right
fringe width. If a fringe width arg is nil, that means to use the
frame's default fringe width. Default fringe widths can be set with
the command `set-fringe-style'.
If optional fourth arg OUTSIDE-MARGINS is non-nil, draw the fringes
outside of the display margins. By default, fringes are drawn between
display marginal areas and the text area.
(fn WINDOW LEFT-WIDTH &optional RIGHT-WIDTH OUTSIDE-MARGINS)