config: further rework for GSSAPI
config: further rework for GSSAPI

GSSAPI_BASE can never be set, did not work with ports OpenSSL /
LibreSSL and now that base kerberos will be gone it doesn't
compile anyway.  We can still switch betweel GSSAPI_HEIMDAL and
GSSAPI_NONE if we require the support or not.

opnsense/tools,opnsense/tools,jamsmartsecurity/tools,OptimEnterprises/tools