Enforced the inclusion of windows headers before nethack headers.

Moved the code page 437 mapping table to winnt.c so that it could be
used in window and console clients.
Added check that fonts support unicode values we use from code page 437.
Use unicode to draw text if font supports it otherwise use ASCII.

sys/winnt/stubs.c

@@ -2,6 +2,7 @@
 /*      Copyright (c) 2015 by Michael Allison              */
 /* NetHack may be freely redistributed.  See license for details. */
 
+#include "win32api.h"
 #include "hack.h"
 
 #ifdef GUISTUB
@@ -52,9 +53,6 @@ char *argv[];
 
 #ifdef TTYSTUB
 
-#include "hack.h"
-#include "win32api.h"
-
 HANDLE hConIn;
 HANDLE hConOut;
 int GUILaunched;