Warn on unknown platforms so we get feedback.
Increase polling SLEEP_POLL_TIMEOUT from 10us to 10ms.

The idea is that if a signal takes time to be delivered, it's because the
system is under heavy load, so don't flood the process. Also a sysadm won't
see thousands of kill lines on his strace logs. The extra delay is
insignificant, this should happen rarely, only when the DB has a PID that is
not cleared.
minor type
typo
gethostname() has non-standard declaration on Solaris 8-9.
INFINITY undefined on Solaris 8
AIX missing strrstr() and mkdtemp()
Merge pull request #483 from jimis/master

minor