For a 'struct window', replace some Lisp_Object fields to

For a 'struct window', replace some Lisp_Object fields to
bitfields where appropriate, remove unused fields.
* window.h (struct window): Remove unused 'last_mark_x' and
'last_mark_y' fields.  Rename 'mini_p' field to 'mini',
change it's type from Lisp_Object to bitfield.
Change type of 'force_start', 'optional_new_start',
'last_had_star', 'update_mode_line' and 'start_at_line_beg'
fields from Lisp_Object to bitfield. Adjust users accordingly.