[libTooling] Move Transformer files to their own directory/library.

Summary:
The Transformer library has been growing inside of
lib/Tooling/Refactoring. However, it's not really related to anything else in
that directory. This revision moves all Transformer-related files into their own
include & lib directories.  A followup revision will (temporarily) add
forwarding headers to help any users migrate their code to the new location.

Reviewers: gribozavr

Subscribers: mgorny, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D68637

llvm-svn: 374271
diff --git a/clang/unittests/Tooling/TransformerTest.cpp b/clang/unittests/Tooling/TransformerTest.cpp
index 5d55182..feae0c6 100644
--- a/clang/unittests/Tooling/TransformerTest.cpp
+++ b/clang/unittests/Tooling/TransformerTest.cpp
@@ -6,9 +6,9 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang/Tooling/Refactoring/Transformer.h"
+#include "clang/Tooling/Transformer/Transformer.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
-#include "clang/Tooling/Refactoring/RangeSelector.h"
+#include "clang/Tooling/Transformer/RangeSelector.h"
 #include "clang/Tooling/Tooling.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/Error.h"