When persistent inventory window is first populated, focus is given to
its window (behavior might be window manager-specific; it happens with
default window manager on OSX).  Focus should be explicitly directed
back to the main window.

More focus:  although the menu window gets focus, the menu inside that
window does not accept focus, so scrolling persistent inventory via
keyboard won't work.  [Does not affect the new '|' command which takes
input via yn_function() rather than directly from the perm_invent menu.]

When persistent inventory window is displayed, an update that ought to
make it grow won't do so even if there is room on the screen for that.
It will add scrollbar(s) when not already there, and it can be resized
manually.

If the permsistent inventory window is manually made taller, it will
fill that space immediately.  But if it is made wider, handling of the
extra space seems to be erratic and it is sometimes left blank until
window is dismissed and re-created via 'i' or toggling 'perm_invent'.

Menus which have entries that are too wide to display have their wide
lines truncated rather than adding a horizontal scrollbar.  Resizing
larger doesn't recover truncated text and resizing smaller truncates
even more.

