track submodule changes for release

.gitmodules

@@ -1,19 +1,19 @@
 [submodule "simgear"]
 	path = simgear
 	url = git://git.code.sf.net/p/flightgear/simgear
-	branch = next
+	branch = release/2016.3
 [submodule "flightgear"]
 	path = flightgear
 	url = git://git.code.sf.net/p/flightgear/flightgear
-	branch = next
+	branch = release/2016.3
 [submodule "fgrun"]
 	path = fgrun
 	url = git://git.code.sf.net/p/flightgear/fgrun
-	branch = next
+	branch = release/2016.3
 [submodule "fgdata"]
 	path = fgdata
 	url = git://git.code.sf.net/p/flightgear/fgdata
-	branch = next
+	branch = release/2016.3
 [submodule "windows-3rd-party"]
 	path = windows-3rd-party
 	url = git://git.code.sf.net/p/flightgear/windows-3rd-party