message: fix types for Windows compiler
diff: @@ -261,10 +261,10 @@ bool introspectAsHDF5File(std::ifstream &f, const std::string &name) noexcept
  bool introspectAsBPFile(std::ifstream &f, const std::string &name) noexcept
  {
  - const size_t MFOOTERSIZE = 56;
  + const int MFOOTERSIZE = 56;
  std::vector<char> buffer(MFOOTERSIZE, 0);
  f.seekg(0, f.end);
  - size_t flength = f.tellg();
  + auto flength = f.tellg();
  if (flength < MFOOTERSIZE)
  {
  return false;
  @@ -363,10 +363,10 @@ bool introspectAsBPDir(const std::string &name) noexcept
  return false;
  }
  - const size_t HEADERSIZE = 64;
  + const int HEADERSIZE = 64;
  std::vector<char> buffer(HEADERSIZE, 0);
  f.seekg(0, f.end);
  - size_t flength = f.tellg();
  + auto flength = f.tellg();
  if (flength >= HEADERSIZE)
  {
  f.seekg(0, f.beg);
  