both $LOGNAME and $USER.
* src/client.c (init_client_options): Use it.
* src/srp-gen.c (make_srp_gen_options): Likewise.
* src/lshd.c (main_argp_parser): Likewise.
* src/lsh-writekey.c (main_argp_parser): Likewise.

Rev: src/client.c:1.165
Rev: src/environ.h.in:1.3
Rev: src/lsh-writekey.c:1.39
Rev: src/lshd.c:1.169
Rev: src/srp-gen.c:1.23