add Reset Speed hotkey. it's bound to Shift+Equals by default because.. well, it's kind of logical... kind of. If you have any better suggestions...

fixes #2154

src/BizHawk.Client.Common/config/Binding.cs

@@ -137,6 +137,7 @@ namespace BizHawk.Client.Common
 						Bind("General", "Smaller Window", "Alt+Down"),
 						Bind("General", "Increase Speed", "Plus"),
 						Bind("General", "Decrease Speed", "Minus"),
+						Bind("General", "Reset Speed", "Shift+Plus"),
 						Bind("General", "Reboot Core", "Ctrl+R"),
 						Bind("General", "Toggle Sound"),
 						Bind("General", "Exit Program"),

src/BizHawk.Client.EmuHawk/MainForm.Hotkey.cs

@@ -120,6 +120,9 @@ namespace BizHawk.Client.EmuHawk
 				case "Increase Speed":
 					IncreaseSpeed();
 					break;
+				case "Reset Speed":
+					ResetSpeed();
+					break;
 				case "Decrease Speed":
 					DecreaseSpeed();
 					break;

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -2498,13 +2498,27 @@ namespace BizHawk.Client.EmuHawk
 
 		private static readonly int[] SpeedPercents = { 1, 3, 6, 12, 25, 50, 75, 100, 150, 200, 300, 400, 800, 1600, 3200, 6400 };
 
+		private bool CheckCanSetSpeed()
+		{
+			if (Config.ClockThrottle)
+				return true;
+			
+			AddOnScreenMessage("Unable to change speed, please switch to clock throttle");
+			return false;
+		}
+
+		private void ResetSpeed()
+		{
+			if (!CheckCanSetSpeed())
+				return;
+
+			SetSpeedPercent(100);
+		}
+
 		private void IncreaseSpeed()
 		{
-			if (!Config.ClockThrottle)
-			{
-				AddOnScreenMessage("Unable to change speed, please switch to clock throttle");
+			if (!CheckCanSetSpeed())
 				return;
-			}
 
 			var oldPercent = Config.SpeedPercent;
 			int newPercent;
@@ -2522,11 +2536,8 @@ namespace BizHawk.Client.EmuHawk
 
 		private void DecreaseSpeed()
 		{
-			if (!Config.ClockThrottle)
-			{
-				AddOnScreenMessage("Unable to change speed, please switch to clock throttle");
+			if (!CheckCanSetSpeed())
 				return;
-			}
 
 			var oldPercent = Config.SpeedPercent;
 			int newPercent;