Bump xos libraries to version 4.0.0

Change-Id: Ib54fef74177ddb18cf530ec2782c81cce3a84a15
diff --git a/VERSION b/VERSION
index 625610e..d72f262 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.3.1-dev
+2.0.0-dev