Port to NetStandard 2.0

[ststeiger]

In order to more easily port ngit to .net-core, could we

0) In NGit\NGit.Util.IO\ThrowingPrintWriter.cs Add public override Encoding Encoding => System.Text.Encoding.UTF8;

within #IF NETFX ?

so it compiles with NETSTANDARD 2.0

As well as making the following changes

A) In Mono.Posix move Remoting to a separate dll ? Mono.Remoting.Channels.Unix

Mono.unix -- deleted remoting

B) Mono.Posix/Mono.Unix.Native/CdeclFunction.cs In CdeclFunction, dispose of

    //this.assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly (
            //      assemblyName, AssemblyBuilderAccess.Run);

                ///* MethodBuilder mb = */ tb.DefinePInvokeMethod (
                //      method, 
                //      library, 
                //      MethodAttributes.PinvokeImpl | MethodAttributes.Static | MethodAttributes.Public,
                //      CallingConventions.Standard, 
                //      returnType, 
                //      parameterTypes, 
                //      CallingConvention.Cdecl,
                //      CharSet.Ansi);
                //mi = tb.CreateType ().GetMethod (method);

In \NSch\Mono.Security\Mono.Security.Protocol.Tls remove the DebugHelper DebugHelper.cs -- removed debug.Lisneter.add

And in NSch\Mono.Security\Mono.Security.Protocol.Tls\HttpsClientStream.cs

somehow replace this code, or make it conditional to full .net framework.

pragma warning disable 618

        //if (ServicePointManager.CertificatePolicy != null) {
        //  ServicePoint sp = _request.ServicePoint;
        //  bool res = ServicePointManager.CertificatePolicy.CheckValidationResult (sp, certificate, _request, _status);
        //  if (!res)
        //      return false;
        //  failed = true;
        //}

Added issues for Mono.Posix and Mono.Security Maybe fork out Mono.Security until the NETSTANDARD port of Mono.Security is ready. Also, fork out Mono.Posix from mono, as there is no nuget-library.

In case anybody needs ngit for NETSTANDARD 2.0: https://github.com/ststeiger/ngit-core