xo-object2: tidy: IPrintable_DList -> list/ subdir

idl/IPrintable_DList.json5

@@ -2,6 +2,7 @@
     mode: "implementation",
     includes: [ "<xo/printable2/Printable.hpp>",
                 "<xo/printable2/detail/IPrintable_Xfer.hpp>" ],
+    local_types: [ ],
     namespace1: "xo",
     namespace2: "scm",
     facet_idl: "idl/Printable.json5",

idl/ISequence_DList.json5

@@ -8,6 +8,5 @@
     brief: "provide ASequence interface for DList state",
     using_doxygen: true,
     repr: "DList",
-    doc: [ "doc for something or other"
-    ],
+    doc: [ "implement ASequence for DList" ],
 }