message: create constant kExpiryUnlimited to match product management request.
diff: #ifndef EXPIRY_H
  #define EXPIRY_H
  +#include <limits.h>
  #include <stdint.h>
  #include "leveldb/env.h"
  #include "leveldb/options.h"
  @@ -58,6 +59,10 @@ public:
  virtual void Dump(Logger * log) const
  {Log(log," Expiry: (none)");};
  + // close to UULONG_MAX, but not equal. UULONG_MAX has meaning
  + // for expiry in FileMetaData object (db/version_edit.h)
  + static const uint64_t kExpiryUnlimited = ULLONG_MAX-2;
  +
  // Quick test to allow manifest logic and such know if
  // extra expiry logic should be checked
  virtual bool ExpiryActivated() const {return(false);};
  