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.

win/X11/winX.c

@@ -98,6 +98,7 @@ void (*input_func)(Widget, XEvent *, String *, Cardinal *);
 int click_x, click_y, click_button; /* Click position on a map window
                                      * (filled by set_button_values()). */
 int updated_inventory; /* used to indicate perm_invent updating */
+color_attr X11_menu_promptstyle = { NO_COLOR, ATR_NONE };
 
 static void X11_error_handler(String) NORETURN;
 static int X11_io_error_handler(Display *);
@@ -1308,7 +1309,18 @@ X11_ctrl_nhwindow(
     int request UNUSED,
     win_request_info *wri UNUSED)
 {
-    return (win_request_info *) 0;
+    if (!wri)
+        return (win_request_info *) 0;
+
+    switch(request) {
+    case set_menu_promptstyle:
+        X11_menu_promptstyle = wri->fromcore.menu_promptstyle;
+        break;
+    default:
+        impossible("invalid request to ctrl_nhwindow: %d", request);
+        break;
+    }
+    return wri;
 }
 
 /* The current implementation has all of the saved lines on the screen. */