Add dump method for selectors

[compnerd]

LGTM

include/clang/Basic/IdentifierTable.h

public:
   
   /// \brief Derive the full selector name (e.g. "foo:bar:") and return
   /// it as an std::string.
   std::string getAsString() const;
 
   /// \brief Prints the full selector name (e.g. "foo:bar:").
   void print(llvm::raw_ostream &OS) const;
 
+  void dump() const;
+
   /// \brief Derive the conventional family of this method.
   ObjCMethodFamily getMethodFamily() const {
     return getMethodFamilyImpl(*this);
   }
   
   ObjCStringFormatFamily getStringFormatFamily() const {
     return getStringFormatFamilyImpl(*this);
   }

lib/Basic/IdentifierTable.cpp

std::string Selector::getAsString() const {
   // We have a multiple keyword selector.
   return getMultiKeywordSelector()->getName();
 }
 
 void Selector::print(llvm::raw_ostream &OS) const {
   OS << getAsString();
 }
 
+LLVM_DUMP_METHOD void Selector::dump() const { print(llvm::errs()); }
+
 /// Interpreting the given string using the normal CamelCase
 /// conventions, determine whether the given string starts with the
 /// given "word", which is assumed to end in a lowercase letter.
 static bool startsWithWord(StringRef name, StringRef word) {
   if (name.size() < word.size()) return false;
   return ((name.size() == word.size() || !isLowercase(name[word.size()])) &&
           name.startswith(word));
 }