User setup and erlang installation

A bit fiddly, but this lets us run a realistic erlang install script
from userspace, and then re-enter userspace later without wiping the
installation.

debian/destroy_environment

@@ -18,8 +18,10 @@ cleanup_mount() {
 
 if test -e "$ROOT"
 then
-    cleanup_mount "$ROOT/proc"
+    cleanup_mount "$ROOT/dev/pts"
+    cleanup_mount "$ROOT/dev"
     cleanup_mount "$ROOT/sys"
+    cleanup_mount "$ROOT/proc"
     echo "Removing $ROOT"
     rm -r "$ROOT"
 else