Add GSSAPI to authentication info check

[jl-sitnrw]

Fixes #208

On Linux SSPI is not available, but GSSAPI is. Kerberos still works on linux, the easiest way to gain a TGT is using kinit username@DOMAIN if dns is configured probably.

libcurl needs to be compiled with Feature GSS-API, but on most distributions, it is by default.