As part of the tty resize handling revision, code dealing with the
perm_invent window was moved out of tty_destroy_nhwindow() was moved
into a separate routine. The new routine would have been called for
a window of NHW_PERMINVENT, but WIN_INVENT doesn't have that type,
just ordinary NHW_MENU, so the cleanup wasn't happening, resulting in
a memory leak.
4140a0023c