Disable dbd6695 and bc911f8 with SDL < 2.0.6

Requested by @gfgtdf. There is some hope that this commit would fix
crash on exit that a couple of developers have reported.

src/sdl/surface.cpp

@@ -14,8 +14,29 @@
 #include "sdl/surface.hpp"
 
 #include "sdl/rect.hpp"
+#include "sdl/utils.hpp"
 #include "video.hpp"
 
+void surface::free_surface()
+{
+	if(surface_) {
+		/* Workaround for an SDL bug.
+		* SDL 2.0.6 frees the blit map unconditionally in SDL_FreeSurface() without checking
+		* if the reference count has fallen to zero. However, many SDL functions such as
+		* SDL_ConvertSurface() assume that the blit map is present.
+		* Thus, we only call SDL_FreeSurface() if this is the last reference to the surface.
+		* Otherwise we just decrement the reference count ourselves.
+		*
+		* - Jyrki, 2017-09-23
+		*/
+		if(surface_->refcount > 1 && sdl_get_version() >= version_info(2, 0, 6)) {
+			--surface_->refcount;
+		} else {
+			SDL_FreeSurface(surface_);
+		}
+	}
+}
+
 surface_restorer::surface_restorer()
 	: target_(nullptr)
 	, rect_(sdl::empty_rect)

src/sdl/surface.hpp

@@ -80,25 +80,7 @@ class surface
 		surface_ = surf;
 	}
 
-	void free_surface()
-	{
-		if(surface_) {
-			/* Workaround for an SDL bug.
-			 * SDL 2.0.6 frees the blit map unconditionally in SDL_FreeSurface() without checking
-			 * if the reference count has fallen to zero. However, many SDL functions such as
-			 * SDL_ConvertSurface() assume that the blit map is present.
-			 * Thus, we only call SDL_FreeSurface() if this is the last reference to the surface.
-			 * Otherwise we just decrement the reference count ourselves.
-			 *
-			 * - Jyrki, 2017-09-23
-			 */
-			if(surface_->refcount > 1) {
-				--surface_->refcount;
-			} else {
-				SDL_FreeSurface(surface_);
-			}
-		}
-	}
+	void free_surface();
 
 	SDL_Surface* surface_;
 };

src/sdl/utils.cpp

@@ -32,6 +32,13 @@
 
 #include <boost/math/constants/constants.hpp>
 
+version_info sdl_get_version()
+{
+	SDL_version sdl_version;
+	SDL_GetVersion(&sdl_version);
+	return version_info(sdl_version.major, sdl_version.minor, sdl_version.patch);
+}
+
 bool is_neutral(const surface& surf)
 {
 	return (surf->format->BytesPerPixel == 4 &&

src/sdl/utils.hpp

@@ -20,13 +20,16 @@
 #include "color.hpp"
 #include "sdl/surface.hpp"
 #include "utils/math.hpp"
+#include "version.hpp"
 
 #include <SDL.h>
 
 #include <cstdlib>
 #include <map>
 #include <string>
 
+version_info sdl_get_version();
+
 inline void sdl_blit(const surface& src, SDL_Rect* src_rect, surface& dst, SDL_Rect* dst_rect){
 	SDL_BlitSurface(src, src_rect, dst, dst_rect);
 }

src/video.cpp

@@ -19,6 +19,7 @@
 #include "image.hpp"
 #include "log.hpp"
 #include "preferences/general.hpp"
+#include "sdl/utils.hpp"
 #include "sdl/window.hpp"
 #include "sdl/userevent.hpp"
 
@@ -196,9 +197,12 @@ void CVideo::update_framebuffer()
 	if(!frameBuffer) {
 		frameBuffer = fb;
 	} else {
-		// Because SDL has already freed the old framebuffer,
-		// ensure that we won't attempt to free it.
-		frameBuffer.clear_without_free();
+		if(sdl_get_version() >= version_info(2, 0, 6)) {
+			// Because SDL has already freed the old framebuffer,
+			// ensure that we won't attempt to free it.
+			frameBuffer.clear_without_free();
+		}
+
 		frameBuffer.assign(fb);
 	}
 }