index: Add end of support info

manual-build @ dc867926

-Subproject commit 7fed1f90c062fdda0755b63ec07308ea0f11c2c6
+Subproject commit dc867926c6ae71652f6b1b80f42576cbebb53b55

images-translated @ 13a930b9

-Subproject commit 147849e2bf1a74efeae6af59052cb4b7b69d4b2a
+Subproject commit 13a930b9cf7657a39467c12c43a348728189d92d

source/index.rst

@@ -6,7 +6,12 @@
 Mahara 16.10 user manual
 ==================================
 
-This is the user manual for Mahara 16.10, which was released on 21 October 2016. When you see the "New in Mahara 16.10" icon |new in Mahara 16.10|, a feature was introduced in Mahara 16.10 or changed from Mahara 16.04.
+This is the user manual for Mahara 16.10, which was released on 21 October 2016. 
+
+.. warning::
+   Mahara 16.10 is not supported any more as of April 2018. Please install or upgrade to a `supported version of Mahara <https://wiki.mahara.org/index.php/SupportedVersions>`_.
+
+When you see the "New in Mahara 16.10" icon |new in Mahara 16.10|, a feature was introduced in Mahara 16.10 or changed from Mahara 16.04.
 
 .. note::