pgsql: Include where needed

Include <sys/select.h> where needed

<sys/select.h> is required by POSIX.1-2001 to get the prototype of
select(2), but nearly no systems enforce that because older standards
let you get away with including some other headers.  Recent OpenBSD
hacking has removed that frail touch of friendliness, however, which
broke some compiles; fix all the way back to 9.1 by adding the required
standard.  Only vacuumdb.c was reported to fail, but it seems easier to
fix the whole lot in a fell swoop.

Per bug #14334 by Sean Farrell.

Branch
------
REL9_3_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/1f55a050d585db075a85d5157586c65409c89a70

Modified Files
--------------
src/backend/libpq/auth.c              | 3 +++
src/backend/postmaster/pgstat.c       | 3 +++
src/bin/pg_basebackup/pg_basebackup.c | 4 +++-
src/bin/pg_basebackup/receivelog.c    | 3 +++
src/bin/pg_dump/parallel.c            | 4 ++++
src/port/pgsleep.c                    | 3 +++
src/test/examples/testlibpq2.c        | 4 ++++
7 files changed, 23 insertions(+), 1 deletion(-)