Add optimization for >>1k fps scenarios

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -2375,9 +2375,20 @@ namespace BizHawk.Client.EmuHawk
 			}
 		}
 
+		private DateTime _lastMessageCheck = DateTime.MinValue;
+
 		private void CheckMessages()
 		{
-			Application.DoEvents();
+			var currentTime = DateTime.Now;
+			// only check window messages a maximum of once per millisecond
+			// this check is irrelvant for the 99% of cases where fps are <1k
+			// but gives a slight fps boost in those scenarios
+			if ((currentTime - _lastMessageCheck).Milliseconds > 0)
+			{
+				_lastMessageCheck = currentTime;
+				Application.DoEvents();
+			}
+
 			if (ActiveForm != null)
 			{
 				ScreenSaver.ResetTimerPeriodically();