Rename SO_TIMESTAMP* to SO_TIMESTAMP*_OLD

Rename SO_TIMESTAMP* to SO_TIMESTAMP*_OLD

Follow the Linux kernel commit v5.1-rc1~178^2~363^2~8 and rename
these constants everywhere.

* xlat/scmvals.in (SO_TIMESTAMP): Rename to SO_TIMESTAMP_OLD.
(SO_TIMESTAMPNS): Rename to SO_TIMESTAMPNS_OLD.
(SO_TIMESTAMPING): Rename to SO_TIMESTAMPING_OLD.
* xlat/sock_options.in: Likewise.
* xlat/sock_rds_options.in: Likewise.
* msghdr.c (cmsg_socket_printers): Likewise.
(print_scm_timestamp): Rename to print_scm_timestamp_old.
(print_scm_timestampns): Rename to print_scm_timestampns_old.
(print_scm_timestamping): Rename to print_scm_timestamping_old.
* tests/msg_control.c (test_scm_timestamp): Rename SO_TIMESTAMP
to SO_TIMESTAMP_OLD.
(test_scm_timestampns): Rename SO_TIMESTAMPNS to SO_TIMESTAMPNS_OLD.
(test_scm_timestamping): Rename SO_TIMESTAMPING to SO_TIMESTAMPING_OLD.
* tests/sockopt-timestamp.c (main): Rename SO_TIMESTAMP and
SO_TIMESTAMPNS to SO_TIMESTAMP_OLD and SO_TIMESTAMPNS_OLD, respectively.