Use named mutex for EC access synchronisation

This allows other programs (or instances of the same program) to all access the EC synchronously, as long as they use the same mutex name.

YAMDCC.ECAccess/EC.cs

@@ -68,7 +68,8 @@ private enum ECCommand : byte
     /// <summary>
     /// Used to synchronise EC access.
     /// </summary>
-    private static readonly Mutex EcMutex = new();
+    private static readonly Mutex EcMutex = new(false,
+        "EcMutex-{B39C3216-FB5D-431C-8F7B-C94EA01AB855}");
 
     /// <summary>
     /// The underlying driver interface object.