Native GSSAPI Provider not documented in security guides

There is no information on how to configure and use the native GSSAPI provider in the security docs. I can only find information on this feature in the following page in the Native platform GSS integration section of https://docs.oracle.com/javase/7/docs/technotes/guides/security/jgss/jgss-features.html

This is an important feature that should be documented. I recommend adding this section to the current GSSAPI section of the security guides. I also think we should add an entry for the "SunNativeProvider" to the JDK Provider document, as it is a provider that is missing from this doc (I can add more details on what should be in that entry later).