use screen.h instead of sdlscreen.h, etc.

Create grafx2-win32 MSVC++ project
create keycode.h
various fixes

src/keycodes.h

@@ -0,0 +1,29 @@
+/* vim:expandtab:ts=2 sw=2:
+*/
+/*  Grafx2 - The Ultimate 256-color bitmap paint program
+
+    Copyright 2018 Thomas Bernard
+    Copyright 1996-2001 Sunset Design (Guillaume Dorme & Karl Maritaud)
+
+    Grafx2 is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    as published by the Free Software Foundation; version 2
+    of the License.
+
+    Grafx2 is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Grafx2; if not, see <http://www.gnu.org/licenses/>
+*/
+
+#ifndef KEYCODES_H_INCLUDED
+#define KEYCODES_H_INCLUDED
+
+#if defined(USE_SDL) || defined(USE_SDL2)
+#include <SDL.h>
+#endif
+
+#endif