* src/client.cc (get_gpgconf_name): New.
(default_socket_name): Get from gpgconf.
(default_uiserver_name): Use gpgrt_access.
* src/exechelp.c: Include errno.h.
(struct private_membuf_s): New.
(init_membuf, clear_membuf, put_membuf, get_membuf): New. Taken from
gnupg/common/membuf.c
(gpgex_spawn_get_string): New.
* src/registry.h (GPG4WIN_REGKEY_1): New.