Add CXXOperatorArity.Zero enum item for further usage in subsequent code.

src/AST/Method.cs

@@ -16,6 +16,7 @@ namespace CppSharp.AST
 
     public enum CXXOperatorArity
     {
+        Zero,
         Unary,
         Binary
     }

src/Generator/AST/Utils.cs

@@ -224,10 +224,12 @@ namespace CppSharp.AST
     {
         public static CXXOperatorArity ClassifyOperator(Function function)
         {
-            if (function.Parameters.Count == 1)
-                return CXXOperatorArity.Unary;
-
-            return CXXOperatorArity.Binary;
+            switch(function.Parameters.Count)
+            {
+                case 0: return CXXOperatorArity.Zero;
+                case 1: return CXXOperatorArity.Unary;
+                default: return CXXOperatorArity.Binary;
+            }
         }
 
         public static string GetOperatorOverloadPair(CXXOperatorKind kind)