Updates core

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

diff --git a/core b/core
index 75efac4..ff539a0 160000 (submodule)
--- a/core
+++ b/core
@@ -1 +1 @@
-Subproject commit 75efac4b00b47f2700d95f48cba1ed3fbb56435a
+Subproject commit ff539a07a4f86dbb19f43afb190102bdd8d8cf95