message: fix off by one in ilog2
diff: @@ -10,13 +10,9 @@ namespace util {
  unsigned ilog2(uint64_t n) {
  #ifdef __GNUC__
  - return n == 0 ? 0 : (64 - __builtin_clzll(n));
  -#elif defined(_MSC_VER)
  -# ifdef _M_X64
  - return 64 - (unsigned)__lzcnt64(n);
  -# else
  -# error Unknown compiler
  -# endif
  + return n == 0 ? 0 : (63 - __builtin_clzll(n));
  +#elif defined(_MSC_VER) && defined(_M_X64)
  + return 63 - (unsigned)__lzcnt64(n);
  #else
  # error Unknown compiler
  #endif
  