Improve spacing in fixed statement output.

ICSharpCode.NRefactory/CSharp/Ast/ComposedType.cs

@@ -55,6 +55,8 @@ namespace ICSharpCode.NRefactory.CSharp
 				return GetChildrenByRole(PointerRole).Count();
 			}
 			set {
+				if (value < 0)
+					throw new ArgumentOutOfRangeException();
 				int d = this.PointerRank;
 				while (d > value) {
 					GetChildByRole(PointerRole).Remove();

ICSharpCode.NRefactory/CSharp/OutputVisitor/OutputVisitor.cs

@@ -1387,9 +1387,13 @@ namespace ICSharpCode.NRefactory.CSharp
 		{
 			StartNode(fixedStatement);
 			WriteKeyword("fixed");
+			Space(policy.UsingParentheses);
 			LPar();
+			Space(policy.WithinUsingParentheses);
 			fixedStatement.Type.AcceptVisitor(this, data);
+			Space();
 			WriteCommaSeparatedList(fixedStatement.Variables);
+			Space(policy.WithinUsingParentheses);
 			RPar();
 			WriteEmbeddedStatement(fixedStatement.EmbeddedStatement);
 			return EndNode(fixedStatement);