message: print error string if msr handle can't be open on Linux
diff: @@ -238,7 +238,7 @@ MsrHandle::MsrHandle(uint32 cpu) : fd(-1), cpu_id(cpu)
  delete[] path;
  if (handle < 0)
  {
  - std::cerr << "PCM Error: can't open MSR handle for core " << cpu << "\n";
  + std::cerr << "PCM Error: can't open MSR handle for core " << cpu << " (" << strerror(errno) << ")\n";
  std::cerr << "Try no-MSR mode by setting env variable PCM_NO_MSR=1\n";
  throw std::exception();
  }
  