Sizzle: account for external document contexts (such as iframes) in combinator checks...

diff --git a/src/sizzle b/src/sizzle
index ed5c22e10fc42805486ff4e501e0e7e5c4b9546b..8bd4d39b5e6f5fae6d20b25877e51e528ae7de5c 160000 (submodule)
--- a/src/sizzle
+++ b/src/sizzle
@@ -1 +1 @@
-Subproject commit ed5c22e10fc42805486ff4e501e0e7e5c4b9546b
+Subproject commit 8bd4d39b5e6f5fae6d20b25877e51e528ae7de5c