Improved generation of enumerations from macros.

We now keep track if a certain macro has already been generated in an enum and skip it in future calls to GenerateEnumFromMacros.

src/AST/Preprocessor.cs

@@ -49,6 +49,9 @@
         // Contains the macro definition text.
         public string Expression;
 
+        // Backing enumeration if one was generated.
+        public Enumeration Enumeration;
+
         public override T Visit<T>(IDeclVisitor<T> visitor)
         {
             return visitor.VisitMacroDefinition(this);

src/Generator/Library.cs

@@ -136,8 +136,13 @@ namespace CppSharp
                     var match = regex.Match(macro.Name);
                     if (!match.Success) continue;
 
+                    if (macro.Enumeration != null)
+                        continue;
+
                     var item = GenerateEnumItemFromMacro(context, macro);
                     @enum.AddItem(item);
+
+                    macro.Enumeration = @enum;
                 }
 
                 if (@enum.Items.Count > 0)