change references from winnt to windows

rename sys/winnt to sys/windows
move vs (visual studio) folder out of win/win32 and into sys/windows
rename include/ntconf.h to include/windconf.h
rename winnt.c to windsys.c
place visual studio projects into individual subfolders.

This will hopefully resolve GitHub issue #484 as well.

sys/windows/stubs.c

@@ -0,0 +1,193 @@
+/* NetHack 3.7  stubs.c       $NHDT-Date: 1596498317 2020/08/03 23:45:17 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.31 $ */
+/*      Copyright (c) 2015 by Michael Allison              */
+/* NetHack may be freely redistributed.  See license for details. */
+
+#include "win32api.h"
+#include "hack.h"
+
+#ifdef GUISTUB
+#ifdef TTYSTUB
+#error You cannot compile this with both GUISTUB and TTYSTUB defined.
+#endif
+
+int GUILaunched;
+struct window_procs mswin_procs = { "-guistubs" };
+
+#ifdef QT_GRAPHICS
+struct window_procs Qt_procs = { "-guistubs" };
+int qt_tilewidth, qt_tileheight, qt_fontsize, qt_compact_mode;
+#endif
+void
+mswin_destroy_reg(void)
+{
+    return;
+}
+void
+mswin_raw_print_flush(void)
+{
+}
+
+void
+mswin_raw_print(const char *str)
+{
+}
+
+/* MINGW32 has trouble with both a main() and WinMain()
+ * so we move main for the MINGW tty version into this stub
+ * so that it is out of sight for the gui linkage.
+ */
+#ifdef __MINGW32__
+extern char default_window_sys[];
+extern int mingw_main(int argc, char **argv);
+
+int
+main(int argc, char *argv[])
+{
+    boolean resuming;
+
+    resuming = mingw_main(argc, argv);
+    nethack_exit(EXIT_SUCCESS);
+    /*NOTREACHED*/
+    return 0;
+}
+#endif
+
+#endif /* GUISTUB */
+
+/* =============================================== */
+
+#ifdef TTYSTUB
+
+HANDLE hConIn;
+HANDLE hConOut;
+int GUILaunched;
+struct window_procs tty_procs = { "-ttystubs" };
+#ifdef CURSES_GRAPHICS
+char erase_char, kill_char;
+#endif
+
+void
+win_tty_init(int dir)
+{
+    return;
+}
+
+void
+consoletty_open(int mode)
+{
+    return;
+}
+
+int
+xputc(int ch)
+{
+    return 0;
+}
+
+void
+xputs(const char *s)
+{
+    return;
+}
+
+void
+raw_clear_screen(void)
+{
+    return;
+}
+
+void
+clear_screen(void)
+{
+    return;
+}
+
+void
+backsp(void)
+{
+    return;
+}
+
+#ifndef NO_MOUSE_ALLOWED
+void
+toggle_mouse_support(void)
+{
+    return;
+}
+#endif
+
+#ifdef PORT_DEBUG
+void
+win32con_debug_keystrokes(void)
+{
+    return;
+}
+void
+win32con_handler_info(void)
+{
+    return;
+}
+#endif
+
+void
+map_subkeyvalue(char *op)
+{
+    return;
+}
+
+/* this is used as a printf() replacement when the window
+ * system isn't initialized yet
+ */
+void msmsg
+VA_DECL(const char *, fmt)
+{
+    VA_START(fmt);
+    VA_INIT(fmt, const char *);
+    VA_END();
+    return;
+}
+
+/*VARARGS1*/
+void consoletty_error
+VA_DECL(const char *, s)
+{
+    VA_START(s);
+    VA_INIT(s, const char *);
+    VA_END();
+    return;
+}
+
+#ifdef TTY_GRAPHICS
+void
+synch_cursor(void)
+{
+    return;
+}
+#endif
+
+void
+more(void)
+{
+    return;
+}
+
+void
+nethack_enter_consoletty(void)
+{
+    return;
+}
+
+void
+set_altkeyhandler(const char *inName)
+{
+    return;
+}
+
+#if defined(USER_SOUNDS) && defined(TTY_SOUND_ESCCODES)
+void
+play_usersound_via_idx(int idx, int volume)
+{
+}
+#endif /* USER_SOUNDS && TTY_SOUND_ESCCODES */
+
+#endif /* TTYSTUBS */