[CommandLine] Remove redundant initializers for StringRef members

[malcolm.parsons]

Summary

The default constructor for a StringRef stores an empty string.

include/llvm/Support/CommandLine.h

 // The general Option Category (used as default category).
 extern OptionCategory GeneralCategory;
 
 //===----------------------------------------------------------------------===//
 // SubCommand class
 //
 class SubCommand {
 private:
-  StringRef Name = "";
-  StringRef Description = "";
+  StringRef Name;
+  StringRef Description;
 
 protected:
   void registerSubCommand();
   void unregisterSubCommand();
 
 public:
   SubCommand(StringRef Name, StringRef Description = "")
       : Name(Name), Description(Description) {
public:
   void setCategory(OptionCategory &C) { Category = &C; }
   void addSubCommand(SubCommand &S) { Subs.insert(&S); }
 
 protected:
   explicit Option(enum NumOccurrencesFlag OccurrencesFlag,
                   enum OptionHidden Hidden)
       : NumOccurrences(0), Occurrences(OccurrencesFlag), Value(0),
         HiddenFlag(Hidden), Formatting(NormalFormatting), Misc(0), Position(0),
-        AdditionalVals(0), ArgStr(""), HelpStr(""), ValueStr(""),
-        Category(&GeneralCategory), FullyInitialized(false) {}
+        AdditionalVals(0), Category(&GeneralCategory), FullyInitialized(false) {
+  }
 
   inline void setNumAdditionalVals(unsigned n) { AdditionalVals = n; }
 
 public:
   // addArgument - Register this argument with the commandline system.
   //
   void addArgument();