Update core.

Signed-off-by: Raphaël Barrois <raphael.barrois@polytechnique.org>

diff --git a/core b/core
index b2eec29..508c23e 160000 (submodule)
--- a/core
+++ b/core
@@ -1 +1 @@
-Subproject commit b2eec295f4a018ae416566007ff9bda64a5f5734
+Subproject commit 508c23e48c10d9b66cb54b4df9931c94565e4c67