add skeleton of win32 implementation

project/msvc/grafx2-win32.vcxproj

@@ -133,6 +133,7 @@
     <ClCompile Include="..\..\src\transform.c" />
     <ClCompile Include="..\..\src\unicode.c" />
     <ClCompile Include="..\..\src\version.c" />
+    <ClCompile Include="..\..\src\win32screen.c" />
     <ClCompile Include="..\..\src\windows.c" />
   </ItemGroup>
   <ItemGroup>

project/msvc/grafx2-win32.vcxproj.filters

@@ -177,6 +177,9 @@
     <ClCompile Include="..\..\src\windows.c">
       <Filter>Fichiers sources</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\src\win32screen.c">
+      <Filter>Fichiers sources</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\..\src\brush.h">

src/win32screen.c

@@ -0,0 +1,69 @@
+/* vim:expandtab:ts=2 sw=2:
+*/
+/*  Grafx2 - The Ultimate 256-color bitmap paint program
+
+    Copyright 2018 Thomas Bernard
+    Copyright 2008 Yves Rizoud
+    Copyright 2007 Adrien Destugues
+    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/>
+*/
+#include "screen.h"
+
+byte Get_Screen_pixel(int x, int y)
+{
+  return 0;
+}
+
+void Set_Screen_pixel(int x, int y, byte value)
+{
+}
+
+byte* Get_Screen_pixel_ptr(int x, int y)
+{
+  return NULL;
+}
+
+void Screen_FillRect(int x, int y, int w, int h, byte color)
+{
+}
+
+void Update_rect(short x, short y, unsigned short width, unsigned short height)
+{
+}
+
+void Flush_update(void)
+{
+}
+
+void Update_status_line(short char_pos, short width)
+{
+}
+
+int SetPalette(const T_Components * colors, int firstcolor, int ncolors)
+{
+  return 0;
+}
+
+void Clear_border(byte color)
+{
+}
+  
+volatile int Allow_colorcycling = 0;
+
+/// Activates or desactivates file drag-dropping in program window.
+void Allow_drag_and_drop(int flag)
+{
+}