Update xvm-devconfig to version 0.84

Requested by glasgall/root@ATHENA.MIT.EDU

diff --git a/xvm-devconfig b/xvm-devconfig
index 049dc20..5af6a02 160000 (submodule)
--- a/xvm-devconfig
+++ b/xvm-devconfig
@@ -1 +1 @@
-Subproject commit 049dc20b6ff77912a5440d3fc85ce5e5c8cb042f
+Subproject commit 5af6a02428d3061e9fd31a59a710bf07f3bd018d