Backport docs for six assemblies

[gewarren]

Describe the issue or suggestion

System.Resources.Extensions:

• System.Resources.Extensions.DeserializingResourceReader
• System.Resources.Extensions.PreserializedResourceWriter

System.Resources.Writer:

• System.Resources.IResourceWriter (interface)
• System.Resources.ResourceWriter (class)

System.Xml.XPath.XDocument:

• System.Xml.XPath.Extensions
• System.Xml.XPath.XDocumentExtensions

System.Net.NameResolution

• System.Net.Dns:
• System.Net.IPHostEntry

System.Security.Cryptography.ProtectedData:

• System.Security.Cryptography.DataProtectionScope (enum)
• System.Security.Cryptography.ProtectedData (static class)

System.IO.Compression.ZipFile:

• System.IO.Compression.ZipFile (static class)
• System.IO.Compression.ZipFileExtensions (static class)