Use last version of core.

Signed-off-by: Florent Bruneau <florent.bruneau@polytechnique.org>

diff --git a/core b/core
index 5177a1b..2023db9 160000 (submodule)
--- a/core
+++ b/core
@@ -1 +1 @@
-Subproject commit 5177a1b50e47e7d62a66aba9565580af3abf15dd
+Subproject commit 2023db9b717479a0a79cbc0a833985b37ec14814