Document the discrepancy in the mask type for _mm_shuffle_ps

diff --git a/library/stdarch b/library/stdarch
index 311d56cd91609c1c1c0370cbd2ece8e3048653a5..d6822f9c433bd70f786b157f17beaf64ee28d83a 160000 (submodule)
--- a/library/stdarch
+++ b/library/stdarch
@@ -1 +1 @@
-Subproject commit 311d56cd91609c1c1c0370cbd2ece8e3048653a5
+Subproject commit d6822f9c433bd70f786b157f17beaf64ee28d83a