* cygheap.h (cygheap_user::curr_imp_token): Rename from current_token.

	* cygheap.h (cygheap_user::curr_imp_token): Rename from current_token.
	Accommodate changge throughout Cygwin.
	(cygheap_user::imp_token): Rename from token.  Accommodate changge
	throughout Cygwin.
	(rcygheap_user::eimpersonate): Use primary token for impersonation.
	* grp.cc (internal_getgroups): Use primary impersonation token when
	impersonated.
	* security.h (_push_thread_privilege): Use primary impersonation token
	when impersonated.