pgsql-server: Cause the format of BC timestamptz output to be 'datetime

Log Message:
-----------
Cause the format of BC timestamptz output to be 'datetime zone BC' rather
than 'datetime BC zone', because the former is accepted by the timestamptz
input converter while the latter may not be depending on spacing. This
is not a loss of compatibility w.r.t. 7.4 and before, because until very
recently there was never a case where we'd output both zone and 'BC'.

Modified Files:
--------------
pgsql-server/src/backend/utils/adt:
datetime.c (r1.130 -> r1.131)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/adt/datetime.c.diff?r1=1.130&r2=1.131)
pgsql-server/src/test/regress/expected:
horology.out (r1.51 -> r1.52)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/test/regress/expected/horology.out.diff?r1=1.51&r2=1.52)
timestamptz.out (r1.16 -> r1.17)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/test/regress/expected/timestamptz.out.diff?r1=1.16&r2=1.17)