[gtk+] Add a Since tag

[Matthias Clasen <matthiasc src gnome org>]

commit d7e8388e9db5529508204879c59c0e249fe2df5a
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Dec 30 00:38:06 2011 -0500

    Add a Since tag
    
    gtk_css_provider_to_string is a post-3.0 addition.
    Fixes bug 659516

 gtk/gtkcssprovider.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkcssprovider.c b/gtk/gtkcssprovider.c
index 4b8ef52..c635d93 100644
--- a/gtk/gtkcssprovider.c
+++ b/gtk/gtkcssprovider.c
@@ -3293,6 +3293,8 @@ gtk_css_provider_print_colors (GHashTable *colors,
  * this @provider.
  *
  * Returns: a new string representing the @provider.
+ *
+ * Since: 3.2
  **/
 char *
 gtk_css_provider_to_string (GtkCssProvider *provider)