message: check for interrupt from fgets on Windows
  Windows does not have the error EINTR when a blocking syscall is
  interrupted by a signal. The ReadFile API that fgets is implemented
  with instead use ERROR_OPERATION_ABORTED. Check for that after fgets.
diff: @@ -383,6 +383,9 @@ bool IOHandlerEditline::GetLine(std::string &line, bool &interrupted) {
  // fgets twice until this bug is fixed.
  if (fgets(buffer, sizeof(buffer), in) == nullptr &&
  fgets(buffer, sizeof(buffer), in) == nullptr) {
  + // this is the equivalent of EINTR for Windows
  + if (GetLastError() == ERROR_OPERATION_ABORTED)
  + continue;
  #else
  if (fgets(buffer, sizeof(buffer), in) == nullptr) {
  #endif
  