* cygheap.h (enum impersonation): New enum.

	* cygheap.h (enum impersonation): New enum.
	(cygheap_user::token): Delete.
	(cygheap_user::impersonated): Delete.
	(cygheap_user::external_token): New member.
	(cygheap_user::internal_token): New member.
	(cygheap_user::impersonation_state): New member.
	(cygheap_user::issetuid): Modify.
	(cygheap_user::token): New method.
	(cygheap_user::deimpersonate): New method.
	(cygheap_user::reimpersonate): New method.
	(cygheap_user::has_impersonation_tokens): New method.
	(cygheap_user::close_impersonation_tokens): New method.
	* dtable.cc (dtable::vfork_child_dup): Use new cygheap_user methods.
	* fhandler_socket.cc (fhandler_socket::dup): Ditto.
	* fork.cc (fork_child): Ditto.
	(fork_parent): Ditto.
	* grp.cc (internal_getgroups): Ditto.
	* security.cc (verify_token): Ditto.
	(check_file_access): Ditto.
	(cygwin_set_impersonation_token): Detect conflicts. Set
	user.external_token.
	* spawn.cc (spawn_guts): Use new cygheap_user methods.
	* syscalls.cc (seteuid32): Rearrange to use the two tokens
	in cygheap_user.
	(setegid32): Use new cygheap_user methods.
	* uinfo.cc: (internal_getlogin): Ditto.