put perf in its own channel

OpenRA.FileFormats/Support/Timer.cs

@@ -30,7 +30,7 @@ namespace OpenRA.Support
 			var time = sw.ElapsedTime();
 			var dt = time - lastTime;
 			if( dt > 0.0001 )
-				Log.Write("debug", message, dt );
+				Log.Write("perf", message, dt );
 			lastTime = time;
 		}
 	}

OpenRA.Game/Exts.cs

@@ -104,7 +104,7 @@ namespace OpenRA
 				a( x );
 				var dt = sw.ElapsedTime() - t;
 				if( dt > time )
-					Log.Write("debug", text, x, dt * 1000);
+					Log.Write("perf", text, x, dt * 1000);
 			} );
 		}
 	}

OpenRA.Game/Support/Program.cs

@@ -35,6 +35,7 @@ namespace OpenRA
 		{
 			// brutal hack
 			Application.CurrentCulture = CultureInfo.InvariantCulture;
+			Log.AddChannel("perf", "openra.perf.txt", false, false);
 
 			if (Debugger.IsAttached)
 			{