[ast] Added IsStatic property to fields.

src/AST/Field.cs

@@ -10,10 +10,13 @@ namespace CppSharp.AST
 
         public Class Class { get; set; }
 
+        public bool IsStatic { get; set; }
+
         public bool IsBitField { get; set; }
 
         public uint BitWidth { get; set; }
 
+
         public Field()
         {
         }