Make pnacl-bccompress add abbreviations for obvious constants.

include/llvm/Bitcode/NaCl/NaClBitcodeDist.h

 //===- NaClBitcodeDist.h ---------------------------------------*- C++ -*-===//
 //     Maps distributions of values in PNaCl bitcode files.
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
@@ skipping 294 matching lines @@
   virtual void AddRecord(const NaClBitcodeRecord &Record);
 
   /// Adds the BlockID of the given bitcode block to the distribution
   /// map, if applicable (based on the value of method UseBlockID).
   /// Note: Requires that GetStorageKind() == BlockStorage.
   virtual void AddBlock(const NaClBitcodeBlock &Block);
 
   /// Builds the distribution associated with the distribution map.
   /// Warning: The distribution is cached, and hence, only valid while
   /// it's contents is not changed.
-  Distribution *GetDistribution() const {
+  const Distribution *GetDistribution() const {
     if (CachedDistribution == 0) Sort();
     return CachedDistribution;
   }
 
   /// Prints out the contents of the distribution map to Stream.
   void Print(raw_ostream &Stream, const std::string &Indent) const;
 
   void Print(raw_ostream &Stream) const {
     std::string Indent;
     Print(Stream, Indent);
@@ skipping 172 matching lines @@
 GetElement(NaClBitcodeDistValue Value) {
   if (TableMap.find(Value) == TableMap.end()) {
     TableMap[Value] = CreateElement(Value);
   }
   return TableMap[Value];
 }
 
 }
 
 #endif