[gtk+] Add docs for GtkCssSection

[Matthias Clasen <matthiasc src gnome org>]

commit b3c1454dcc6b1f916390db55dcc9673027b79659
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Dec 25 22:22:51 2015 -0500

    Add docs for GtkCssSection

 gtk/gtkcsssection.h |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkcsssection.h b/gtk/gtkcsssection.h
index 4f88eee..1bb04d0 100644
--- a/gtk/gtkcsssection.h
+++ b/gtk/gtkcsssection.h
@@ -66,6 +66,12 @@ typedef enum
   GTK_CSS_SECTION_KEYFRAMES
 } GtkCssSectionType;
 
+/**
+ * GtkCssSection:
+ *
+ * GtkCssSection is an auxiliary object containing information about
+ * the results of parsing a CSS style sheet.
+ */
 typedef struct _GtkCssSection GtkCssSection;
 
 GDK_AVAILABLE_IN_3_2