Support server side delegation

[behackett]

It should be possible to support server side delegation using the ImpersonateSecurityContext and RevertSecurityContext functions in SSPI.

https://docs.microsoft.com/en-us/windows/desktop/api/sspi/nf-sspi-impersonatesecuritycontext
https://docs.microsoft.com/en-us/windows/desktop/api/sspi/nf-sspi-revertsecuritycontext
https://docs.microsoft.com/en-us/windows/desktop/SecAuthN/context-requirements

The API work to match ccs-pykerberos:

• Add support for the "delegated" param to authGSSClientInit
• Add support for authGSSServerHasDelegated

I don't think the other related functions (authGSSServerStoreDelegate and authGSSServerCacheName) make sense in SSPI or are possible to replicate.