[gtksourceview] docs: no API changes in 3.99.3

[Sébastien Wilmet <swilmet src gnome org>]

commit 8cc7e5bdeaf7083c1d6bb9f63a4da46e126727dc
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Thu Mar 30 20:08:53 2017 +0200

    docs: no API changes in 3.99.3
    
    It's better to mention it because otherwise people might think that the
    porting guide is incomplete.

 docs/reference/porting-guide.xml |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/porting-guide.xml b/docs/reference/porting-guide.xml
index f60243c..c7d11ce 100644
--- a/docs/reference/porting-guide.xml
+++ b/docs/reference/porting-guide.xml
@@ -128,6 +128,11 @@
   </refsect1>
 
   <refsect1>
+    <title>GtkSourceView 3.99.3</title>
+    <para>No API changes.</para>
+  </refsect1>
+
+  <refsect1>
     <title>GtkSourceView 3.99.4</title>
     <itemizedlist>
       <listitem>