I think this fixes all problems with the boundary boz drawn around
perm_invent. Also, if you enabled perm_invent in inuse_only mode
while there are already more items in use than would fix in the
available number of lines, it wasn't switching to two columns until
the next update_inventory(). And the new color handling wasn't
incorporate into tty_refresh_inventory() so after a corner window
clobbered some of perm_invent, it got redrawn but without color,
again until the next update_inventory().
With any luck this fixes more bugs than it introduces....
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