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.

win/win32/mhfont.h

@@ -9,6 +9,7 @@
 
 #include "winMS.h"
 
+BOOL mswin_font_supports_unicode(HFONT hFont);
 HGDIOBJ mswin_get_font(int win_type, int attr, HDC hdc, BOOL replace);
 void mswin_init_splashfonts(HWND hWnd);
 void mswin_destroy_splashfonts(void);