message: Clear the last error before calling Mb2Wc in ConvertToW
  When the console functional tests are running on OneCoreUAP, the
  newly-introduced (65bd4e327, FillOutputCharacterA tests will
  actually fail because of radio interference on the return value of GLE.
  Fixes
diff: @@ -38,6 +38,13 @@ static const WORD leftShiftScanCode = 0x2A;
  THROW_IF_FAILED(SizeTToInt(source.size(), &iSource));
  // Ask how much space we will need.
  + // In certain codepages, Mb2Wc will "successfully" produce zero characters (like in CP50220, where a SHIFT-IN character
  + // is consumed but not transformed into anything) without explicitly failing. When it does this, GetLastError will return
  + // the last error encountered by the last function that actually did have an error.
  + // This is arguably correct (as the documentation says "The function returns 0 if it does not succeed"). There is a
  + // difference that we **don't actually care about** between failing and successfully producing zero characters.,
  + // Anyway: we need to clear the last error so that we can fail out and IGNORE_BAD_GLE after it inevitably succeed-fails.
  + SetLastError(0);
  int const iTarget = MultiByteToWideChar(codePage, 0, source.data(), iSource, nullptr, 0);
  THROW_LAST_ERROR_IF_AND_IGNORE_BAD_GLE(0 == iTarget);
  