Passes the given remote_token to the mechanism.
This wraps GSS_Process_context_token according to RFC 2743
section 2.2.4.
This is used for tokens that are received outside the
handshaking between GSS_Init_sec_context
(GSSAPI.InitContext.init ) and GSS_Accept_sec_context
(GSSAPI.AcceptContext.accept ).
An example is when GSSAPI.InitContext.init returns a final
token and flags the context as established, but the acceptor
context detects an error and sends a failure token back. That
token is processed using this function since
GSSAPI.InitContext.init doesn't handle any more tokens by
then.