Add a new window-port interface function
perminvent_info *
update_invent_slot(winid window, int slot, perminvent_info *);
That should be nice and flexible and allow exchanges of useful
information between the core and the window port. Information
to be exchange can be easily modified in include/wintype.h as
things evolve.
Information useful to the core can be exchanged from the
window-port in struct to_core.
Information useful from the core to the window-port can be
passed in struct from_core.
I'm not going to update any docs until much later after things
are fully working and settled.
This also doesn't fix or have anything to do with existing
TTY_PERM_INVENT issues.
736e9f14f8