Added an Std.Map wrapper to be able to use it in internal declarations.

src/Generator/Types/Std/Stdlib.cs

@@ -231,6 +231,9 @@ namespace CppSharp.Types.Std
 
         public override string CSharpSignature(CSharpTypePrinterContext ctx)
         {
+            if (ctx.CSharpKind == CSharpTypePrinterContextKind.Native)
+                return "Std.Map";
+
             var type = Type as TemplateSpecializationType;
             return string.Format("System.Collections.Generic.Dictionary<{0}, {1}>",
                 type.Arguments[0].Type, type.Arguments[1].Type);

src/Runtime/StdMap.cs

@@ -0,0 +1,11 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Std
+{
+    [StructLayout(LayoutKind.Sequential)]
+    public unsafe struct Map
+    {
+
+    }
+}