Add missing availability note

git-svn-id: http://svn.osgeo.org/postgis/trunk@14277 b70326c6-7e19-0410-871a-916f4a2858ee

Author: robe2

doc/reference_constructor.xml

@@ -1060,7 +1060,7 @@ SELECT
 
  <para>Creates a LineString from an Encoded Polyline string.</para>
  <para>See http://developers.google.com/maps/documentation/utilities/polylinealgorithm</para>
-
+ <para>Availability: 2.2.0</para>
  </refsection>
 
  <refsection>