Reintroduce the serialization library, with fixed dependencies.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@111279 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/FrontendActions.cpp b/lib/Frontend/FrontendActions.cpp
index 0a03ab4..8599efb 100644
--- a/lib/Frontend/FrontendActions.cpp
+++ b/lib/Frontend/FrontendActions.cpp
@@ -17,8 +17,8 @@
 #include "clang/Frontend/ASTUnit.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendDiagnostic.h"
-#include "clang/Frontend/PCHWriter.h"
 #include "clang/Frontend/Utils.h"
+#include "clang/Serialization/PCHWriter.h"
 #include "llvm/ADT/OwningPtr.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"