flags.sortloot tweaks

flags.sortloot tweaks

flags.sortloot was changed from boolean to xchar, but proper type
is plain char.  (Presumeably it was originally off or on, then got
changed to 'n' for off, 'l' for on, plus 'f' for super-on.)

Also, make the sortloot menu for 'O' mark the current value as
preselected when interactively setting the value.  (I've been
meaning to do this for various other options but haven't gotten
around to it.  The need to workaround PICK_ONE+MENU_SELECTED menu
behavior is a nuisance.)