Add -DSDL2 for Win32/OSX support (untested), print SDL2 usage on startup

The quake2 binary now gets -DSDL2 in the CFLAGS, so Win32/OSX can
use different #include paths accordingly.
This is also (ab)used to print which SDL version is used on startup.
Don't use this for anything else, use
#if SDL_VERSION_ATLEAST(2, 0, 0)
instead.

I haven't tested building on/for Win32 or OSX, there may be more
work to do.

Furthermore I added Copyright-Info about CalculateGammaRamp()
in refresh.c (it's from SDL2)

Makefile

@@ -163,7 +163,6 @@ endif
 # Extra CFLAGS for SDL
 ifneq ($(OSTYPE), Windows)
 ifeq ($(OSTYPE), Darwin)
-# TODO: set -I.../SDL2/ or /SDL/
 SDLCFLAGS :=
 else # not darwin
 ifeq ($(WITH_SDL2),yes)
@@ -219,17 +218,24 @@ endif
 
 # Extra LDFLAGS for SDL
 ifeq ($(OSTYPE), Windows)
-# TODO: SDL2 for win/osx
+ifeq ($(WITH_SDL2),yes)
+SDLLDFLAGS := -lSDL2
+else # not SDL2
 SDLLDFLAGS := -lSDL
+endif # SDL2
 else ifeq ($(OSTYPE), Darwin)
+ifeq ($(WITH_SDL2),yes)
+SDLLDFLAGS := -framework SDL2 -framework OpenGL -framework Cocoa
+else # not SDL2
 SDLLDFLAGS := -framework SDL -framework OpenGL -framework Cocoa
-else
+endif # SDL2
+else # not Darwin/Win
 ifeq ($(WITH_SDL2),yes)
 SDLLDFLAGS := $(shell sdl2-config --libs)
-else
+else # not SDL2
 SDLLDFLAGS := $(shell sdl-config --libs)
-endif
-endif
+endif # SDL2
+endif # Darwin/Win
 
 # ----------
 
@@ -348,6 +354,10 @@ release/quake2.exe : CFLAGS += -DRETEXTURE
 release/quake2.exe : LDFLAGS += -ljpeg
 endif 
 
+ifeq ($(WITH_SDL2),yes)
+release/quake2.exe : CFLAGS += -DSDL2
+endif
+
 release/quake2.exe : LDFLAGS += -mwindows -lopengl32
 else
 client:
@@ -409,6 +419,10 @@ release/quake2 : LDFLAGS += -ljpeg
 endif
 endif
 
+ifeq ($(WITH_SDL2),yes)
+release/quake2 : CFLAGS += -DSDL2
+endif
+ 
 ifeq ($(OSTYPE), Darwin)
 ifeq ($(OSX_APP), yes)
 release/quake2 : LDFLAGS += -Xlinker -rpath -Xlinker @loader_path/../Frameworks

src/backends/sdl/input.c

@@ -29,13 +29,15 @@
 #include "../../client/header/keyboard.h"
 #include "../generic/header/input.h"
 
-#ifdef _WIN32
+#if defined(_WIN32) || defined(__APPLE__)
+#ifdef SDL2
+#include <SDL2/SDL.h>
+#else // SDL1.2
 #include <SDL/SDL.h>
-#elif defined(__APPLE__)
-#include <SDL/SDL.h>
-#else
+#endif //SDL2
+#else // not _WIN32 || APPLE
 #include <SDL.h>
-#endif
+#endif // _WIN32 || APPLE
 
 #if SDL_VERSION_ATLEAST(2, 0, 0)
 	#define SDLK_KP0 SDLK_KP_0

src/backends/sdl/refresh.c

@@ -18,6 +18,11 @@
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  * 02111-1307, USA.
  *
+ * ----------------------------------------------------------------------
+ * CalculateGammaRamp() is derived from SDL2's SDL_CalculateGammaRamp()
+ * (C) 1997-2013 Sam Lantinga <slouken@libsdl.org>
+ * Published under zlib License: http://www.libsdl.org/license.php
+ *
  * =======================================================================
  *
  * This file implements an OpenGL context via SDL
@@ -32,13 +37,15 @@
 #include <GL/gl.h>
 #endif
 
-#ifdef _WIN32
+#if defined(_WIN32) || defined(__APPLE__)
+#ifdef SDL2
+#include <SDL2/SDL.h>
+#else // SDL1.2
 #include <SDL/SDL.h>
-#elif defined(__APPLE__)
-#include <SDL/SDL.h>
-#else
+#endif //SDL2
+#else // not _WIN32 || APPLE
 #include <SDL.h>
-#endif
+#endif // _WIN32 || APPLE
 
 /* The window icon */
 #include "icon/q2icon.xbm"

src/backends/sdl/sound.c

@@ -34,13 +34,15 @@
  */
 
 /* SDL includes */
-#ifdef _WIN32
+#if defined(_WIN32) || defined(__APPLE__)
+#ifdef SDL2
+#include <SDL2/SDL.h>
+#else // SDL1.2
 #include <SDL/SDL.h>
-#elif defined(__APPLE__)
-#include <SDL/SDL.h>
-#else
+#endif //SDL2
+#else // not _WIN32 || APPLE
 #include <SDL.h>
-#endif
+#endif // _WIN32 || APPLE
 
 /* Local includes */
 #include "../../client/header/client.h"

src/backends/unix/main.c

@@ -77,6 +77,12 @@ main(int argc, char **argv)
 
 #ifndef DEDICATED_ONLY
 	printf("Client build options:\n");
+#ifdef SDL2
+	printf(" + SDL2\n");
+#else
+	printf(" - SDL2 (using 1.2)\n");
+#endif
+
 #ifdef CDA
 	printf(" + CD audio\n");
 #else

src/backends/windows/system.c

@@ -712,6 +712,11 @@ WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
 
 #ifndef DEDICATED_ONLY
 	printf("Client build options:\n");
+#ifdef SDL2
+	printf(" + SDL2\n");
+#else
+	printf(" - SDL2 (using 1.2)\n");
+#endif
 #ifdef CDA
 	printf(" + CD audio\n");
 #else