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.Mods.RA/Widgets/BuildPaletteWidget.cs

@@ -191,8 +191,8 @@ namespace OpenRA.Mods.RA.Widgets
 			if (!IsVisible()) return;
 			// TODO: fix
 
-			int paletteHeight = DrawPalette(CurrentQueue);
-			DrawBuildTabs(world, paletteHeight);
+			DrawPalette(CurrentQueue);
+			DrawBuildTabs(world);
 		}
 
 		int numActualRows = 5;
@@ -413,7 +413,7 @@ namespace OpenRA.Mods.RA.Widgets
 				Game.GetModifierKeys().HasModifier(Modifiers.Shift) ? 5 : 1));
 		}
 
-		void DrawBuildTabs(World world, int paletteHeight)
+		void DrawBuildTabs(World world)
 		{
 			const int tabWidth = 24;
 			const int tabHeight = 40;
@@ -450,7 +450,7 @@ namespace OpenRA.Mods.RA.Widgets
 			}
 		}
 
-		void DrawRightAligned(string text, int2 pos, Color c)
+		static void DrawRightAligned(string text, int2 pos, Color c)
 		{
 			var font = Game.Renderer.Fonts["Bold"];
 			font.DrawText(text, pos - new int2(font.Measure(text).X, 0), c);