General uncontroversial cleanup:

- Made private methods static where possible (runtime can elide checking the object for null).
- Declared attribute classes as sealed (allows reflection on attributes to complete faster).
- Moved some static cctor's into field initializers (static cctor's are slower than static field initializers).
- Made classes static if they contained only static methods (can't create instances of useless objects).
- Use inferable Exts.Lazy and not new Lazy<T>().
- Added required STAThread attribute to CrashDialog.
- Removed unused parameters in private methods.
- Added Serializable attribute to exceptions.
- Added parameter name in calls to ArgumentNullException.
- Use of as operator instead of is + cast.
- Changed (x as Foo).Bar anti-pattern into ((Foo)x).Bar. Results in sensible cast exceptions on error rather than null dereferences.
- Removed unused method in NullShader.

OpenRA.Game/Network/OrderManager.cs

@@ -145,12 +145,12 @@ namespace OpenRA.Network
 			throw new InvalidOperationException("Out of sync in frame {0}.\n {1}\n Compare syncreport.log with other players.".F(frame, orders.ElementAt(index).Order.ToString()));
 		}
 
-		void OutOfSync(int frame)
+		static void OutOfSync(int frame)
 		{
 			throw new InvalidOperationException("Out of sync in frame {0}.\n Compare syncreport.log with other players.".F(frame));
 		}
 
-		void OutOfSync(int frame, string blame)
+		static void OutOfSync(int frame, string blame)
 		{
 			throw new InvalidOperationException("Out of sync in frame {0}: Blame {1}.\n Compare syncreport.log with other players.".F(frame, blame));
 		}

OpenRA.Game/Network/ReplayRecorderConnection.cs

@@ -86,7 +86,7 @@ namespace OpenRA.Network
 				});
 		}
 
-		bool IsGameStart(byte[] data)
+		static bool IsGameStart(byte[] data)
 		{
 			if (data.Length == 5 && data[4] == 0xbf)
 				return false;

OpenRA.Game/Network/UPnP.cs

@@ -14,7 +14,7 @@ using Mono.Nat;
 
 namespace OpenRA.Network
 {
-	public class UPnP
+	public static class UPnP
 	{
 		public static INatDevice NatDevice;