don't use SDL in Load_surface() anymore

So the init phase does not depend on SDL anymore.

Signed-off-by: Thomas Bernard <miniupnp@free.fr>

src/gfx2surface.h

@@ -0,0 +1,46 @@
+/* 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/>
+*/
+//////////////////////////////////////////////////////////////////////////////
+///@file gfx2surface.h
+/// Memory representation of a 8bits picture
+//////////////////////////////////////////////////////////////////////////////
+
+#ifndef GFX2SURFACE_H__
+#define GFX2SURFACE_H__
+
+#include "struct.h"
+
+/// to load 256 color pictures into memory
+typedef struct
+{
+  byte * pixels;
+  T_Palette palette;
+  word w;           ///< Width
+  word h;           ///< Height
+} T_GFX2_Surface;
+
+T_GFX2_Surface * New_GFX2_Surface(word width, word height);
+void Free_GFX2_Surface(T_GFX2_Surface * surface);
+
+byte Get_GFX2_Surface_pixel(const T_GFX2_Surface * surface, int x, int y);
+void Set_GFX2_Surface_pixel(T_GFX2_Surface * surface, int x, int y, byte value);
+
+#endif