* linux-nat.c (my_waitpid): New function.

	(linux_test_for_tracefork): Make more robust and verbose.  Take
	an ORIGINAL_PID argument and test for PTRACE_SETOPTIONS first.
	(linux_supports_tracefork, linux_supports_tracevforkdone): Take a PID
	argument.  Update calls to linux_test_for_tracefork.
	(linux_enable_event_reporting, child_follow_fork)
	(child_insert_fork_catchpoint, child_insert_vfork_catchpoint)
	(child_insert_exec_catchpoint): Update calls to
	linux_supports_tracefork and linux_supports_tracevforkdone.