app: Add docs to GimpSessionInfo related classes

app/widgets/gimpsessioninfo-aux.h

@@ -22,6 +22,10 @@
 #define __GIMP_SESSION_INFO_AUX_H__
 
 
+/**
+ * Contains arbitrary data in the session management system, used for
+ * example by dockables to manage dockable-specific data.
+ */
 struct _GimpSessionInfoAux
 {
   gchar *name;

app/widgets/gimpsessioninfo-book.h

@@ -22,6 +22,10 @@
 #define __GIMP_SESSION_INFO_BOOK_H__
 
 
+/**
+ * Contains information about a book (a GtkNotebook of dockables) in
+ * the interface.
+ */
 struct _GimpSessionInfoBook
 {
   gint   position;

app/widgets/gimpsessioninfo-dockable.h

@@ -22,6 +22,9 @@
 #define __GIMP_SESSION_INFO_DOCKABLE_H__
 
 
+/**
+ * Contains information about a dockable in the interface.
+ */
 struct _GimpSessionInfoDockable
 {
   gchar        *identifier;

app/widgets/gimpsessioninfo.h

@@ -35,6 +35,10 @@
 
 typedef struct _GimpSessionInfoClass  GimpSessionInfoClass;
 
+/**
+ * Contains session info for one toplevel window in the interface such
+ * as a dock, the empty-image-window, or the open/save dialog.
+ */
 struct _GimpSessionInfo
 {
   GimpObject              parent_instance;