drop unused parameter on IGraphicsDevice.Clear()

OpenRA.FileFormats/Graphics/IGraphicsDevice.cs

@@ -42,7 +42,7 @@ namespace OpenRA.FileFormats.Graphics
 		Size WindowSize { get; }
 		int GpuMemoryUsed { get; }
 
-		void Clear( Color color );
+		void Clear();
 		void Present();
 		void PumpInput(IInputHandler inputHandler);
 

OpenRA.Game/Graphics/Renderer.cs

@@ -75,7 +75,7 @@ namespace OpenRA.Graphics
 
 		public void BeginFrame(float2 scroll, float zoom)
 		{
-			device.Clear(Color.Black);
+			device.Clear();
 
 			WorldLineRenderer.LineWidth = zoom;
 			float2 r1 = new float2(2f/Resolution.Width, -2f/Resolution.Height);

OpenRA.Renderer.Cg/GraphicsDevice.cs

@@ -99,7 +99,7 @@ namespace OpenRA.Renderer.Cg
 			ErrorHandler.CheckGlError();
 		}
 
-		public void Clear( Color c )
+		public void Clear()
 		{
 			Gl.glClearColor( 0, 0, 0, 0 );
 			ErrorHandler.CheckGlError();

OpenRA.Renderer.Gl/GraphicsDevice.cs

@@ -79,7 +79,7 @@ namespace OpenRA.Renderer.Glsl
 			ErrorHandler.CheckGlError();
 		}
 
-		public void Clear( Color c )
+		public void Clear()
 		{
 			Gl.glClearColor( 0, 0, 0, 0 );
 			ErrorHandler.CheckGlError();

OpenRA.Renderer.Null/NullGraphicsDevice.cs

@@ -38,7 +38,7 @@ namespace OpenRA.Renderer.Null
 		public void EnableScissor(int left, int top, int width, int height) { }
 		public void DisableScissor() { }
 
-		public void Clear(Color c) { }
+		public void Clear() { }
 
 		public void Present() { }
 		public void PumpInput(IInputHandler ih)