into LSSUSPENDED state, have that LWP save its PCU state for the coredump and
release its PCU status since its probably going to be exiting very soon.
Make pcu_save_all tolerate for being called for non-curlwp if that lwp belongs
to the same process, has a state of LSSUSPENDED, and no PCUs are in use.
Make the MD coredump code use pcu_save_all(l) since it'll need to save all
the PCU state anyways and can take advantage of the above tests.
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