alternative to display_inventory for window-port

Several window ports that support perm_invent were
using a call back to the core display_inventory()
function.

While calling from the window port back to core functions
is arguably not ideal in the first place, it was recently
brought to light that code NetHack-3.7 code changes to
display_inventory() actually caused it to stop repopulating
the perm_invent window as intended under certain circumstances.

For now, provide an alternative function, repopulate_perminvent(),
that hopefullshould still work the way it did previously.

There will likely be some additional changes after this to
further improve things, at some point.

For now though, this
Resolves #1454

include/extern.h

@@ -1358,6 +1358,7 @@ extern void sync_perminvent(void);
 extern void perm_invent_toggled(boolean negated);
 extern void prepare_perminvent(winid window);
 extern struct obj *carrying_stoning_corpse(void);
+extern void repopulate_perminvent(void);
 
 /* ### ioctl.c ### */