[gtk+] textview: Fix "Since" versions after backport

[Rico Tzschichholz <ricotz src gnome org>]

commit 9ca8b71e76234fb68a1273fa7420e8aac63590f3
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Wed Mar 25 20:52:43 2015 +0100

    textview: Fix "Since" versions after backport
    
    Fix for 28063ee2e42e7ce47b7bd5326f2d53875a377d57 which got cherry-picked
    to 3.16

 gtk/gtktexttag.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/gtk/gtktexttag.c b/gtk/gtktexttag.c
index 9296275..58ab9fa 100644
--- a/gtk/gtktexttag.c
+++ b/gtk/gtktexttag.c
@@ -534,7 +534,7 @@ gtk_text_tag_class_init (GtkTextTagClass *klass)
    * color may be applied instead of the foreground. Setting this property
    * will always override those defaults.
    *
-   * Since: 3.18
+   * Since: 3.16
    */
   g_object_class_install_property (object_class,
                                    PROP_UNDERLINE_RGBA,
@@ -550,7 +550,7 @@ gtk_text_tag_class_init (GtkTextTagClass *klass)
    * This property modifies the color of strikeouts. If not set, strikeouts
    * will use the forground color.
    *
-   * Since: 3.18
+   * Since: 3.16
    */
   g_object_class_install_property (object_class,
                                    PROP_STRIKETHROUGH_RGBA,
@@ -792,7 +792,7 @@ gtk_text_tag_class_init (GtkTextTagClass *klass)
    *
    * If the #GtkTextTag:underline-rgba property has been set.
    *
-   * Since: 3.18
+   * Since: 3.16
    */
   ADD_SET_PROP ("underline-rgba-set", PROP_UNDERLINE_RGBA_SET,
                 P_("Underline RGBA set"),
@@ -803,7 +803,7 @@ gtk_text_tag_class_init (GtkTextTagClass *klass)
    *
    * If the #GtkTextTag:strikethrough-rgba property has been set.
    *
-   * Since: 3.18
+   * Since: 3.16
    */
   ADD_SET_PROP ("strikethrough-rgba-set", PROP_STRIKETHROUGH_RGBA_SET,
                 P_("Strikethrough RGBA set"),