Update core (fix stupid error in PlFilterGroupeableOrder)

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

diff --git a/core b/core
index 7c44b8b..85bb0c6 160000 (submodule)
--- a/core
+++ b/core
@@ -1 +1 @@
-Subproject commit 7c44b8bc211c768efdb3be75c5a7057bf0e5663e
+Subproject commit 85bb0c6fe8cca537d48c297476971cdac5a7065f