Don't emit "virtual" modifier in interfaces (C# 8 default interface members).

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -1396,7 +1396,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 						m |= Modifiers.Abstract;
 					if (member.IsOverride)
 						m |= Modifiers.Override;
-					if (member.IsVirtual && !member.IsAbstract && !member.IsOverride)
+					if (member.IsVirtual && !member.IsAbstract && !member.IsOverride && declaringType.Kind != TypeKind.Interface)
 						m |= Modifiers.Virtual;
 					if (member.IsSealed)
 						m |= Modifiers.Sealed;

ICSharpCode.Decompiler/Documentation/IdStringProvider.cs

@@ -352,7 +352,6 @@ namespace ICSharpCode.Decompiler.Documentation
 				typeParameterCount = ReflectionHelper.ReadTypeParameterCount(typeName, ref pos);
 			} else if (pos < typeName.Length && typeName[pos] == '{') {
 				// bound generic type
-				typeArguments = new List<ITypeReference>();
 				do {
 					pos++;
 					typeArguments.Add(ParseTypeName(typeName, ref pos));