Add support for PPP authentication cookie

[jeff-winn]

Need to add support for PPP authentication cookies during a dialing request. This should involve the fSkipPppAuth flag on the RASDIALEXTENSIONS structure along with adding .NET based implementation of the RASDEVSPECIFICINFO structure.

Potential class name: PppAuthenticationCookie
Requires storage of a byte array of unknown size.

https://msdn.microsoft.com/en-us/library/windows/desktop/aa377029(v=vs.85).aspx
https://docs.microsoft.com/en-us/windows/desktop/api/ras/ns-ras-tagrasdevspecificinfo

[jeff-winn]

Need someone with this network requirement to test the feature as its being built. If you have this need, please leave a response.