Remove duplicate comment
Use wrapper for pdwait4()

For platforms that don't implement pdwait4(), simulate
with wait4(pdgetpid())
Restructure procdesc tests
Track which signals are received
Add notes on future tests
Tidy up process descriptor tests

Remove duplicate tests.
Remove unnecessary clear of errno.
Comment clarifications.
Clear process descriptor on close.
Generalize test fixture for PD_DAEMON use
Improve procdesc fixture

Check no SIGCHLD and clean up more thoroughly
Test /proc/<pid>/fdinfo contents for process descriptor
Expect a single reap for zombies
No process descriptors left => normal process
Reap all children in procdesc tests

Want to ensure that later tests don't end up reaping
the children of earlier tests.
Fix SIGCHLD tests.

Also remove markers of previously failing operations
Check pdkill() on reaped process gives error
Check that invalid signal numbers are bounced
Reap sub-processes in namespace/pdfork test
Check expected child process states
Add more tests for NS/pdfork interactions