Remove a whole lot of unused variables

There are about 30 removed in this patch, generated by a new FixIt I haven't
got round to submitting yet.

llvm-svn: 195814

clang/lib/Frontend/CompilerInvocation.cpp

@@ -1763,7 +1763,6 @@ std::string CompilerInvocation::getModuleHash() const {
   const HeaderSearchOptions &hsOpts = getHeaderSearchOpts();
   code = hash_combine(code, ppOpts.UsePredefines, ppOpts.DetailedRecord);
 
-  std::vector<StringRef> MacroDefs;
   for (std::vector<std::pair<std::string, bool/*isUndef*/> >::const_iterator 
             I = getPreprocessorOpts().Macros.begin(),
          IEnd = getPreprocessorOpts().Macros.end();