Use langversion 5 for .NET Core project.

Author: drieseng

src/Renci.SshNet.NETCore/Renci.SshNet.NETCore.csproj

@@ -6,6 +6,7 @@
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <AssemblyName>Renci.SshNet</AssemblyName>
     <AssemblyOriginatorKeyFile>../Renci.SshNet.snk</AssemblyOriginatorKeyFile>
+    <LangVersion>5</LangVersion>
     <SignAssembly>true</SignAssembly>
     <PublicSign Condition=" '$(OS)' != 'Windows_NT' ">true</PublicSign>
     <GenerateAssemblyTitleAttribute>false</GenerateAssemblyTitleAttribute>