[clang] minor cleanup in clang/tooling/refactoring

[alexander-shaposhnikov]

Summary

1. Add missing explicit.
2. Add missing std::move

(return type is Expected<std::vector<AtomicChange>> but we return std::vector<AtomicChange>, so cast to && is necessary).

Test plan: make check-all

[arphaman]

LGTM

cfe/trunk/include/clang/Tooling/Refactoring/Rename/SymbolName.h

 /// methods can contain multiple argument lables:
 ///
 /// \code
 /// - (void) myMethodNamePiece: (int)x anotherNamePieces:(int)y;
 /// //       ^~ string 0 ~~~~~         ^~ string 1 ~~~~~
 /// \endcode
 class SymbolName {
 public:
-  SymbolName(StringRef Name) {
+  explicit SymbolName(StringRef Name) {
     // While empty symbol names are valid (Objective-C selectors can have empty
     // name pieces), occurrences Objective-C selectors are created using an
     // array of strings instead of just one string.
     assert(!Name.empty() && "Invalid symbol name!");
     this->Name.push_back(Name.str());
   }
 
   ArrayRef<std::string> getNamePieces() const { return Name; }

cfe/trunk/lib/Tooling/Refactoring/Rename/RenamingAction.cpp

for (const auto &Range : llvm::enumerate(Ranges)) {
       auto Error =
           Change.replace(SM, CharSourceRange::getCharRange(Range.value()),
                          NewNameStrings[Range.index()]);
       if (Error)
         return std::move(Error);
     }
     Changes.push_back(std::move(Change));
   }
-  return Changes;
+  return std::move(Changes);
 }
 
 /// Takes each atomic change and inserts its replacements into the set of
 /// replacements that belong to the appropriate file.
 static void convertChangesToFileReplacements(
     ArrayRef<AtomicChange> AtomicChanges,
     std::map<std::string, tooling::Replacements> *FileToReplaces) {
   for (const auto &AtomicChange : AtomicChanges) {