(preserve_other_columns, preserve_my_columns): Use new

(preserve_other_columns, preserve_my_columns): Use new
macros WINDOW_LEFT_MARGIN and WINDOW_RIGHT_EDGE.
(adjust_window_charstarts, verify_charstarts, cancel_my_columns):
Use new macro WINDOW_LEFT_MARGIN instead of w->left.
(direct_output_for_insert, direct_output_forward_char): Likewise.
(buffer_posn_from_coords): Likewise.
(verify_charstarts): Use new macro WINDOW_FULL_WIDTH_P.
(update_frame): For determining when to wrap the cursor, use the
new macro FRAME_WINDOW_WIDTH instead of FRAME_WIDTH; they aren't
necessarily the same any more.
(change_frame_size_1): Use FRAME_WINDOW_WIDTH to check for changes.
Give `set_window_width' the window width value.  Use new macro SET_FRAME_WIDTH.