Update LLVM for rebase to r212749.

Includes a cherry-pick of:
r212948 - fixes a small issue with atomic calls

Change-Id: Ib97bd980b59f18142a69506400911a6009d9df18
diff --git a/lib/CodeGen/SelectionDAG/ResourcePriorityQueue.cpp b/lib/CodeGen/SelectionDAG/ResourcePriorityQueue.cpp
index f92230c..624003f 100644
--- a/lib/CodeGen/SelectionDAG/ResourcePriorityQueue.cpp
+++ b/lib/CodeGen/SelectionDAG/ResourcePriorityQueue.cpp
@@ -442,7 +442,7 @@
     ResCount -= (regPressureDelta(SU) * ScaleTwo);
   }
 
-  // These are platform specific things.
+  // These are platform-specific things.
   // Will need to go into the back end
   // and accessed from here via a hook.
   for (SDNode *N = SU->getNode(); N; N = N->getGluedNode()) {