dirmngr: Default to a user socket name and enable autostart.
* common/homedir.c (dirmngr_socket_name): Rename to dirmngr_sys_socket_name. (dirmngr_user_socket_name): New. * common/asshelp.c (start_new_dirmngr): Handle sys and user dirmngr socket. * dirmngr/dirmngr.c (main): Ditto. * dirmngr/server.c (cmd_getinfo): Ditto. * sm/server.c (gpgsm_server): Ditto. * dirmngr/dirmngr-client.c (start_dirmngr): Likewise. * tools/gpgconf.c (main): Print "dirmngr-sys-socket" with --list-dirs. * configure.ac (USE_DIRMNGR_AUTO_START): Set by default.