Update Doxygen Documentation

 * Update README with notification about dropping support
   for Ubuntu 16.04
 * Update cross-compile guide

Signed-off-by: Jan Eilers <jan.eilers@arm.com>
Change-Id: I10b89ba09bc5737012557eacdeaacc620ccdb8a9
diff --git a/21.02/classarmnn_1_1_fully_connected_layer-members.xhtml b/21.02/classarmnn_1_1_fully_connected_layer-members.xhtml
index 6714242..e7579bd 100644
--- a/21.02/classarmnn_1_1_fully_connected_layer-members.xhtml
+++ b/21.02/classarmnn_1_1_fully_connected_layer-members.xhtml
@@ -176,7 +176,7 @@
 <!-- start footer part -->
 <div id="nav-path" class="navpath"><!-- id is needed for treeview function! -->
   <ul>
-    <li class="footer">Generated on Thu Feb 25 2021 17:27:58 for ArmNN by
+    <li class="footer">Generated on Fri Mar 19 2021 15:26:11 for ArmNN by
     <a href="http://www.doxygen.org/index.html">
     <img class="footer" src="doxygen.png" alt="doxygen"/></a> 1.8.13 </li>
   </ul>