Add two new properties IsOverride and IsProxy to methods.

These can be useful to provide "fake" declarations in the AST whose implementation is written by the user later with a MethodBody block. Since this is so useful for custom bindings a simplified abstraction for this will be added in the future.

src/AST/Method.cs

@@ -76,6 +76,8 @@ namespace CppSharp.AST
         public bool IsConst { get; set; }
         public bool IsImplicit { get; set; }
         public bool IsSynthetized { get; set; }
+        public bool IsOverride { get; set; }
+        public bool IsProxy { get; set; }
 
         public CXXMethodKind Kind;
         public CXXOperatorKind OperatorKind;