Checkpoint/Restart for Linux.
* linux-nat.c: Add support for debugging multiple forks.
Add #include for linux-fork.h (interface spec).
(super_mourn_inferior): New function pointer.
(child_mourn_inferior): New function / target method.
(linux_target): Claim to_mourn_inferior method pointer.
(child_follow_fork): Call interface to linux-fork, conditionally
add new fork processes to list of debugged processes.
(kill_inferior): Use interface to linux-fork to kill
multiple processes.
* linux-fork.h: New file.
* linux-fork.c: New file. Support for debugging multiple forks
of the same program. Support for checkpoint and restart commands.
* infrun.c (nullify_last_target_wait_ptid): New function.
* Makefile.in: Add linux-fork.
* config/*/linux.mh: Add linux-fork.
* NEWS: Mention new functionality.
