Added selection of frame buffer implementation in Cocoa backend

Added vid_glswfb CVAR but set it to false by default for compatibility reasons

src/posix/cocoa/i_video.mm

@@ -116,6 +116,11 @@ - (void)enterFullscreenOnZoom
 
 DFrameBuffer *CreateGLSWFrameBuffer(int width, int height, bool bgra, bool fullscreen);
 
+CUSTOM_CVAR(Bool, vid_glswfb, false, CVAR_NOINITCALL)
+{
+	Printf("This won't take effect until " GAMENAME " is restarted.\n");
+}
+
 EXTERN_CVAR(Bool, ticker   )
 EXTERN_CVAR(Bool, vid_vsync)
 EXTERN_CVAR(Bool, vid_hidpi)
@@ -551,9 +556,12 @@ - (void)setCursor:(NSCursor*)cursor
 
 	// Create OpenGL pixel format
 
-	NSOpenGLPixelFormat* pixelFormat = CreatePixelFormat(OpenGLProfile::Core);
+	const OpenGLProfile defaultProfile = (1 == vid_renderer || vid_glswfb)
+		? OpenGLProfile::Core
+		: OpenGLProfile::Legacy;
+	NSOpenGLPixelFormat* pixelFormat = CreatePixelFormat(defaultProfile);
 
-	if (nil == pixelFormat)
+	if (nil == pixelFormat && OpenGLProfile::Core == defaultProfile)
 	{
 		pixelFormat = CreatePixelFormat(OpenGLProfile::Legacy);
 
@@ -647,11 +655,14 @@ - (void)setCursor:(NSCursor*)cursor
  	{
 		fb = new OpenGLFrameBuffer(NULL, width, height, 32, 60, fullscreen);
 	}
-	else
+	else if (vid_glswfb)
 	{
-		//fb = new CocoaFrameBuffer(width, height, bgra, fullscreen);
 		fb = CreateGLSWFrameBuffer(width, height, bgra, fullscreen);
 	}
+	else
+	{
+		fb = new CocoaFrameBuffer(width, height, bgra, fullscreen);
+	}
 
 	fb->SetFlash(flashColor, flashAmount);