* cygheap.h: Move `token' and `impersonated' from class _pinfo

    * cygheap.h: Move `token' and `impersonated' from class _pinfo
        to class cygheap_user.
        * pinfo.h: Ditto.
        * fork.cc (fork_child): Change usage of `token' and `impersonated'
        accordingly.
        (fork_parent): Ditto.
        * security.cc (cygwin_set_impersonation_token): Ditto.
        * sigproc.cc (proc_subproc): Ditto.
        * spawn.cc (spawn_guts): Ditto.
        * syscalls.cc (seteuid): Ditto.
        * uinfo.cc (uinfo_init): Ditto.