Correctly clean up the created OpenGL objects created for the slider rendering.

This is necessary because the OpenGL context being closed does apparently not close
the process and the game can be restarted with another resolution without shutting
down the process completely.

src/itdelatrisu/opsu/render/CurveRenderState.java

@@ -75,6 +75,12 @@ public class CurveRenderState {
 		//scale = scale * 118 / 128; //for curves exactly as big as the sliderball
 		FrameBufferCache.init(width, height);
 	}
+	
+	public static void shutdown()
+	{
+		staticState.shutdown();
+		FrameBufferCache.shutdown();
+	}
 
 	/**
 	 * Creates an object to hold the render state that's necessary to draw a curve.
@@ -447,5 +453,25 @@ public class CurveRenderState {
 				colBorderLoc = GL20.glGetUniformLocation(program, "col_border");
 			}
 		}
+
+		private void shutdown()
+		{
+			if(gradientTexture != 0)
+			{
+			GL11.glDeleteTextures(gradientTexture);
+			gradientTexture = 0;
+			}
+			
+			if(program != 0)
+			{
+				GL20.glDeleteProgram(program);
+				program = 0;
+				attribLoc = 0;
+				texCoordLoc = 0;
+				colLoc = 0;
+				colBorderLoc = 0;
+				texLoc = 0;
+			}
+		}
 	}
 }