[gtk+] Add some docs to GtkIcon

[Matthias Clasen <matthiasc src gnome org>]

commit 2d6ce0da0838b416e3693f9ba4320a24dc5fbcbd
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Dec 22 14:22:13 2015 -0500

    Add some docs to GtkIcon

 gtk/gtkicon.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkicon.c b/gtk/gtkicon.c
index 06c19dc..3e5e80f 100644
--- a/gtk/gtkicon.c
+++ b/gtk/gtkicon.c
@@ -25,6 +25,10 @@
 #include "gtkiconprivate.h"
 #include "gtkwidgetprivate.h"
 
+/* GtkIcon is a minimal widget wrapped around a GtkBuiltinIcon gadget,
+ * It should be used whenever builtin-icon functionality is desired
+ * but a widget is needed for other reasons.
+ */
 enum {
   PROP_0,
   PROP_CSS_NAME,