System.OutOfMemoryException from CsvParser.FillBuffer

[michaeldahlke]

Describe the bug
Trying to read a very large file that is not correctly formatted as CSV may result in an out of memory exception when calling Read().

To Reproduce

// create a large file using cmd.exe
// fsutil file createnew 1gb.tst 1073741824

const string filePath = @"C:\1gb.tst";

try
{
    using (var stream = File.OpenRead(filePath))
    {
        using (var csvReader = new CsvReader(new StreamReader(stream), CultureInfo.InvariantCulture))
        {
            csvReader.Read();
        }
    }
}
catch (CsvHelperException)
{
    // pass
}
catch (OutOfMemoryException)
{
    // fail
}

Expected behavior
CsvHelper does not use an excessive amount of memory and a more appropriate exception such as BadDataException is thrown.