Fix Linux/OSX HTTPS, OpenSSL, .NET Core bug

[nopara73]

.NET Core behaves differently on Windows and Linux. Maybe wait until it gets fixed?

3de217f

SslStream httpsStream;
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
	httpsStream = new SslStream(stream, leaveInnerStreamOpen: true);
else // TODO: Fix this security vulnerability
{
	httpsStream = new SslStream(
		stream,
		leaveInnerStreamOpen: true,
		userCertificateValidationCallback: (a, b, c, d) => true);
}

[nopara73]

Made it optional and default false: SocksPortHandler.IgnoreSslCertification

[nopara73]

Should be fixed in .NET Core and not just hacked around.
Issue opened: https://github.com/dotnet/corefx/issues/21761

[nopara73]

Need .NET Core SNI feature: https://github.com/dotnet/corefx/issues/9608

[nopara73]

Fixed in .NET Core 3.1: https://github.com/nopara73/SslStreamBugCore3