* lin-lwp.c (struct lwp_info): Add member `resumed'.

* lin-lwp.c (struct lwp_info): Add member `resumed'.
(iterate_over_lwps): Make sure we can handle CALLBACK deleting the
LWP it's called for.
(lin_lwp_attach): Mark LWP as resumed to make sure the fake
SIGSTOP is reported.
(resume_clear_callback): New function.
(resume_set_callback): New function.
(lin_lwp_resume): Mark all LWP's that we're going to resume as
resumed, and unmark all others.
(status_callback): Only report a pending wait status if we pretend
that LP has been resumed.
(resumed_callback): New function.
(lin_lwp_wait): Add assertions to check that LWP's are properly
marked as resumed.  Partially revert 2001-05-25 patch by Michael
Snyder: do not resume all threads.  Add comment explaining the
problems associated with this bit of code.