build: bump libbson

Christian Hergert · Christian Hergert · commit 8d377f93d7d6 · 2014-06-23T12:00:53.000-07:00
diff --git a/src/libbson b/src/libbson
@@ -1 +1 @@
-Subproject commit b0814fe6e592812b75643e32e1f68fcd2870bb00
+Subproject commit 640d89b6d8c9e605c54606cb6f06b150a0b46596
