Add config flag for using InvariantCulture across all threads

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

@@ -438,5 +438,7 @@ public void SetWindowScaleFor(string sysID, int windowScale)
 		public int AVWriterResizeHeight { get; set; } = 0;
 
 		public int AVWriterResizeWidth { get; set; } = 0;
+
+		public bool SetInvariantCulture { get; set; } = false;
 	}
 }

src/BizHawk.Client.EmuHawk/Program.cs

@@ -1,6 +1,7 @@
 using System.Diagnostics;
 using System.IO;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.InteropServices;
@@ -183,6 +184,12 @@ private static int SubMain(string[] args)
 			if (initialConfig.SaveSlot is 0) initialConfig.SaveSlot = 10; //TODO remove after a while
 			// initialConfig should really be globalConfig as it's mutable
 
+			//TODO ideally this should happen as early as possible, which means parsing the config earlier, which means parsing the command-line flags earlier... actually there's not that much else above this --yoshi
+			if (initialConfig.SetInvariantCulture)
+			{
+				CultureInfo.CurrentCulture = CultureInfo.DefaultThreadCurrentCulture = CultureInfo.InvariantCulture;
+			}
+
 			StringLogUtil.DefaultToDisk = initialConfig.Movies.MoviesOnDisk;
 
 			// must be done VERY early, before any SDL_Init calls can be done