Move Extract.cpp that wasn't moved in r317343

llvm-svn: 317344
diff --git a/clang/lib/Tooling/Refactoring/Extract.cpp b/clang/lib/Tooling/Refactoring/Extract/Extract.cpp
similarity index 100%
rename from clang/lib/Tooling/Refactoring/Extract.cpp
rename to clang/lib/Tooling/Refactoring/Extract/Extract.cpp