* configure.host: Set gdb_host_cpu to sh for all sh*.
(sh*-*-netbsdelf*): New host.
* configure.tgt: Set gdb_target_cpu to sh for all sh*.
(sh*-*-netbsdelf*): New target.
* sh-nbsd-nat.c: New file.
* sh-nbsd-tdep.c: New file.
* sh-nbsd-tdep.h: New file.
* config/sh/nbsd.mh: New file.
* config/sh/nbsd.mt: New file.
* config/sh/nm-nbsd.h: New file.
* config/sh/tm-nbsd.h: New file.