use ctrl_nhwindow() for menu prompt style

This implements the mechanics to use the ctrl_nhwindow() interface
capability to pass down a setting change from the core to the active
window port, without resorting to accessing a core global variable
from within the window port, and without altering the interface..

The passed setting is honored in the tty and curses window ports.

X11 and mswin receive and store the values, but no implementation
to change the menu prompt style is there yet.

Qt does not store the values or have an implementation.

The setting change is done in allmain.c immediately after
creating the WIN_INVEN window.

src/invent.c

@@ -45,7 +45,6 @@ static void itemactions_pushkeys(struct obj *, int);
 static void mime_action(const char *);
 
 /* enum and structs are defined in wintype.h */
-static win_request_info zerowri = { { 0L, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0 } };
 static win_request_info wri_info;
 static int perminv_flags = InvOptNone;
 static boolean in_perm_invent_toggled;