pgsql: Revert "Use pselect(2) not select(2), if available, to wait in p

Revert "Use pselect(2) not select(2), if available, to wait in postmaster's loop."

This reverts commit 81069a9efc5a374dd39874a161f456f0fb3afba4.

Buildfarm results suggest that some platforms have versions of pselect(2)
that are not merely non-atomic, but flat out non-functional. Revert the
use-pselect patch to confirm this diagnosis (and exclude the no-SA_RESTART
patch as the source of trouble). If it's so, we should probably look into
blacklisting specific platforms that have broken pselect.

Discussion: https://postgr.es/m/9696.1493072081@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/64925603c972aa3a9f1d4c42686dba67f1a7e9d0

Modified Files
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configure | 2 +-
configure.in | 2 +-
src/backend/postmaster/postmaster.c | 63 ++++++++++---------------------------
src/include/pg_config.h.in | 3 --
src/include/pg_config.h.win32 | 3 --
5 files changed, 19 insertions(+), 54 deletions(-)