[gxml] Documented TwDocument namespaces handling

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit 2ac9cce0a792b24c28a4a2e4262ed02929867799
Author: Daniel Espinosa <esodan gmail com>
Date:   Wed May 13 18:46:13 2015 -0500

    Documented TwDocument namespaces handling

 gxml/TwDocument.vala |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)
---
diff --git a/gxml/TwDocument.vala b/gxml/TwDocument.vala
index 9f3ec64..b6114cf 100644
--- a/gxml/TwDocument.vala
+++ b/gxml/TwDocument.vala
@@ -35,6 +35,20 @@ public class GXml.TwDocument : GXml.TwNode, GXml.Document
     this.file = f;
   }
   // GXml.Node
+  /**
+   * { inheritDoc}
+   *
+   * All namespaces are stored at { link GXml.Node.namespaces} owned by
+   * this { link GXml.TwDocument}.
+   *
+   * First namespace at list, is considered default one for the document. If
+   * you haven't declared a namespace for this document or for its root element,
+   * and you define one for a child node, this one is added for the first time
+   * to document's namespaces, then this becomes the default namespace. To avoid
+   * this, you should set a namespace for documento or its root, then childs.
+   *
+   * Default { link GXml.Namespace} for a document is the first
+   */
   public override bool set_namespace (string uri, string? prefix)
   {
     _namespaces.add (new TwNamespace (this, uri, prefix));