bump libbson to 1.5.2

bjori · bjori · commit 9be7c0d519bd · 2017-01-10T11:25:44.000-08:00
diff --git a/src/libbson b/src/libbson
@@ -1 +1 @@
-Subproject commit db718e2d3a10f7ad7368fff98c94987eaffde357
+Subproject commit 8694565e795e8bb9e7f60dee623d377518796fc1
