[ThinLTO] Use decimal suffix for promoted values to match demanglers

[tejohnson]

Summary

Demanglers such as libiberty know how to strip suffixes of the form
\.[a-zA-Z]+\.\d+, but our current promoted value suffixes are
.llvm.${modulehash}, where the module hash is in hex. Change the
module hash to decimal to allow demanglers to handle this.

include/llvm/IR/ModuleSummaryIndex.h

const ModuleHash &getModuleHash(const StringRef ModPath) const {
     return It->second.second;
   }
 
   /// Convenience method for creating a promoted global name
   /// for the given value name of a local, and its original module's ID.
   static std::string getGlobalNameForLocal(StringRef Name, ModuleHash ModHash) {
     SmallString<256> NewName(Name);
     NewName += ".llvm.";
-    NewName += utohexstr(ModHash[0]); // Take the first 32 bits
+    NewName += utostr(ModHash[0]); // Take the first 32 bits
     return NewName.str();
   }
 
   /// Helper to obtain the unpromoted name for a global value (or the original
   /// name if not promoted).
   static StringRef getOriginalNameBeforePromote(StringRef Name) {
     std::pair<StringRef, StringRef> Pair = Name.split(".llvm.");
     return Pair.first;