Allocate temporary TOKEN_GROUP arrays using TLS

Allocate temporary TOKEN_GROUP arrays using TLS

A user token can be up to 64K in size.  The group list might take a lot
of that so use tmp_pathbuf allocated space rather than stack space
allocted via alloca.  In create_token the TOKEN_GROUP was allocated via
malloc, but the code is needlessly complicated.  Simplify by using
tmp_pathbuf as well.

	* sec_auth.cc (verify_token): Allocate TOKEN_GROUP via tmp_pathbuf.
	(create_token): Ditto.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>