* marker.c (set_marker_internal): If desired position is passed

* marker.c (set_marker_internal): If desired position is passed
as a marker, avoid call to buf_charpos_to_bytepos.
* window.c (Fset_window_point): Omit redundant type checking.
(Fset_window_start): Likewise.  Format comment.
(window_scroll_pixel_based): Use set_marker_restricted_both
with character and byte positions obtained from an iterator.
(Fset_window_configuration): Use set_marker_restricted_both.
* xdisp.c (message_dolog): Likewise.