update debian packaging to qt5/python3

debian/changelog

@@ -1,6 +1,7 @@
-qgis (2.999.0) UNRELEASED; urgency=medium
+qgis (2.99.0) UNRELEASED; urgency=medium
 
   * New development version 2.999 after branch of 2.16
+  * move to qt5/python3
 
  -- Jürgen E. Fischer <jef@norbit.de>  Fri, 08 Jul 2016 14:12:36 +0200
 

debian/compat.in

@@ -1,3 +1,2 @@
-#stretch sid jessie trusty wily xenial#9
-#wheezy jessie#8
-#precise#7
+#stretch sid jessie trusty xenial#9
+#jessie#8