[gtk+] Add a deprecation note

[Matthias Clasen <matthiasc src gnome org>]

commit b90ae2cfbfe7f1701b9f6bfc4a95f24390d0ab3c
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon May 23 20:40:03 2016 -0400

    Add a deprecation note
    
    Mark GtkWidget:style property as deprecated in the docs.

 gtk/gtkwidget.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 36752b4..5b0e280 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -1239,6 +1239,13 @@ gtk_widget_class_init (GtkWidgetClass *klass)
 
 G_GNUC_BEGIN_IGNORE_DEPRECATIONS
 
+  /**
+   * GtkWidget:style:
+   *
+   * The style of the widget, which contains information about how it will look (colors, etc).
+   *
+   * Deprecated: Use #GtkStyleContext instead
+   */
   widget_props[PROP_STYLE] =
       g_param_spec_object ("style",
                            P_("Style"),