Build is broken with libstroke

[Peter TB Brett]

Commit 8f62bf59258 (http://git.gedaproject.org/geda-gaf/commit/?id=8f62bf59258800492a26bd9521283550ada1ecf0) removed the GschemToplevel.window member. Unfortunately, this is used in the libstroke support code, which wasn't fixed up.

x_stroke.c: In function ‘x_stroke_record’:
x_stroke.c:105:30: error: ‘GschemToplevel’ has no member named ‘window’
     gdk_draw_point (w_current->window, view_gc, x, y);
                              ^