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/tools/bugpoint/OptimizerDriver.cpp b/tools/bugpoint/OptimizerDriver.cpp
index b2722e6..d452fd9 100644
--- a/tools/bugpoint/OptimizerDriver.cpp
+++ b/tools/bugpoint/OptimizerDriver.cpp
@@ -129,7 +129,7 @@
   // setup the output file name
   outs().flush();
   SmallString<128> UniqueFilename;
-  error_code EC = sys::fs::createUniqueFile(
+  std::error_code EC = sys::fs::createUniqueFile(
       OutputPrefix + "-output-%%%%%%%.bc", UniqueFilename);
   if (EC) {
     errs() << getToolName() << ": Error making unique filename: "