Bump version to v1.7.2

Prepare for a new release.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

VERSION.txt

diff --git a/VERSION.txt b/VERSION.txt
index 943f9cb..f8a696c 100644
--- a/VERSION.txt
+++ b/VERSION.txt
@@ -1 +1 @@
-1.7.1
+1.7.2