Fix #600: variable called int should be displayed as @int

ICSharpCode.Decompiler/Ast/TextTokenWriter.cs

@@ -53,6 +53,10 @@ namespace ICSharpCode.Decompiler.Ast
 		
 		public override void WriteIdentifier(Identifier identifier)
 		{
+			if (identifier.IsVerbatim || CSharpOutputVisitor.IsKeyword(identifier.Name, identifier)) {
+				output.Write('@');
+			}
+			
 			var definition = GetCurrentDefinition();
 			if (definition != null) {
 				output.WriteDefinition(identifier.Name, definition, false);

NRefactory/ICSharpCode.NRefactory.CSharp/OutputVisitor/CSharpOutputVisitor.cs

@@ -1158,7 +1158,7 @@ namespace ICSharpCode.NRefactory.CSharp
 			StartNode(attributeSection);
 			WriteToken(Roles.LBracket);
 			if (!string.IsNullOrEmpty(attributeSection.AttributeTarget)) {
-				WriteIdentifier(attributeSection.AttributeTargetToken);
+				WriteKeyword(attributeSection.AttributeTarget, Roles.Identifier);
 				WriteToken(Roles.Colon);
 				Space();
 			}