Fix #13894: CSS identifiers with backslash-escaped whitespace

(cherry picked from commit a75016634d439179fa6517da1918a5a667886e99)

diff --git a/src/sizzle b/src/sizzle
index 1728f0199bd5b7b3b33082487ff9815e3af80e1c..00a7e0d8d66fb7915a24a2270033b8efc9e9c774 160000 (submodule)
--- a/src/sizzle
+++ b/src/sizzle
@@ -1 +1 @@
-Subproject commit 1728f0199bd5b7b3b33082487ff9815e3af80e1c
+Subproject commit 00a7e0d8d66fb7915a24a2270033b8efc9e9c774