[glib] docs: add Since for g_str_to_ascii

[David King <davidk src gnome org>]

commit 18fe6d83125f2cd2a3e355396f90ea979e42b37d
Author: David King <amigadave amigadave com>
Date:   Sun Jan 10 23:20:37 2016 +0000

    docs: add Since for g_str_to_ascii

 glib/gtranslit.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/glib/gtranslit.c b/glib/gtranslit.c
index 5831456..c9f07f8 100644
--- a/glib/gtranslit.c
+++ b/glib/gtranslit.c
@@ -323,6 +323,8 @@ get_default_item_id (void)
  * @from_locale.
  *
  * Returns: a string in plain ASCII
+ *
+ * Since: 2.40
  **/
 gchar *
 g_str_to_ascii (const gchar *str,