Fixed the generation of anonymous types to consider parenting anonymous types.

Signed-off-by: Dimitar Dobrev <dpldobrev@yahoo.com>

src/Generator/Passes/CleanInvalidDeclNamesPass.cs

@@ -35,7 +35,7 @@ namespace CppSharp.Passes
             // types with empty names are assumed to be private
             if (decl is Class && string.IsNullOrWhiteSpace(decl.Name))
             {
-                decl.Name = "_";
+                decl.Name = decl.Namespace.Name == "_" ? "__" : "_";
                 decl.ExplicitlyIgnore();
                 return false;
             }

tests/Basic/Basic.h

@@ -561,3 +561,13 @@ public:
 };
 
 DLL_API void va_listFunction(va_list v);
+
+struct DLL_API TestEmptyName
+{
+    struct
+    {
+        struct
+        {
+        };
+    };
+};