build: bump libbson for json and keylen check

Christian Hergert · Christian Hergert · commit 7a39ff58ceda · 2014-06-18T20:07:06.000-07:00
diff --git a/src/libbson b/src/libbson
@@ -1 +1 @@
-Subproject commit be892a87c5706895508dbc6123ed8ce722c239e5
+Subproject commit af039f005c509b04f47dde05e0d545e810213159
