Lua - implement emu.enablerewind(), also add on screen message when rewind is toggled

BizHawk.MultiClient/LuaImplementation.cs

@@ -291,6 +291,7 @@ namespace BizHawk.MultiClient
 			"minimizeframeskip",
 			"limitframerate",
 			"displayvsync",
+			"enablerewind"
 		};
 
 		public static string[] MemoryFunctions = new string[]
@@ -898,6 +899,23 @@ namespace BizHawk.MultiClient
 			}
 		}
 
+		public void emu_enablerewind(object boolean)
+		{
+			string temp = boolean.ToString();
+			if (!String.IsNullOrWhiteSpace(temp))
+			{
+				if (temp == "0" || temp.ToLower() == "false")
+				{
+					Global.Config.RewindEnabled = false;
+				}
+				else
+				{
+					Global.Config.RewindEnabled = true;
+				}
+				Global.MainForm.RewindMessage();
+			}
+		}
+
 		public void emu_frameskip(object num_frames)
 		{
 			try

BizHawk.MultiClient/MainForm.MenuItems.cs

@@ -476,6 +476,19 @@ namespace BizHawk.MultiClient
 		private void enableRewindToolStripMenuItem_Click(object sender, EventArgs e)
 		{
 			Global.Config.RewindEnabled ^= true;
+			RewindMessage();
+		}
+
+		public void RewindMessage()
+		{
+			if (Global.Config.RewindEnabled)
+			{
+				Global.OSD.AddMessage("Rewind enabled");
+			}
+			else
+			{
+				Global.OSD.AddMessage("Rewind disabled");
+			}
 		}
 
 		private void hexEditorToolStripMenuItem_Click(object sender, EventArgs e)