pgsql: Consistently declare timestamp variables as TimestampTz.

Consistently declare timestamp variables as TimestampTz.

Twiddle the replication-related code so that its timestamp variables
are declared TimestampTz, rather than the uninformative "int64" that
was previously used for meant-to-be-always-integer timestamps.
This resolves the int64-vs-TimestampTz declaration inconsistencies
introduced by commit 7c030783a, though in the opposite direction to
what was originally suggested.

This required including datatype/timestamp.h in a couple more places
than before. I decided it would be a good idea to slim down that
header by not having it pull in <float.h> etc, as those headers are
no longer at all relevant to its purpose. Unsurprisingly, a small number
of .c files turn out to have been depending on those inclusions, so add
them back in the .c files as needed.

Discussion: https://postgr.es/m/26788.1487455319@sss.pgh.pa.us
Discussion: https://postgr.es/m/27694.1487456324@sss.pgh.pa.us

Branch
------
master

Details
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http://git.postgresql.org/pg/commitdiff/c29aff959dc64f7321062e7f33d8c6ec23db53d3

Modified Files
--------------
contrib/auth_delay/auth_delay.c | 2 ++
contrib/btree_gist/btree_ts.c | 2 ++
src/backend/access/common/reloptions.c | 2 ++
src/backend/access/transam/xlog.c | 1 +
src/backend/commands/prepare.c | 2 ++
src/backend/executor/nodeBitmapHeapscan.c | 2 ++
src/backend/replication/basebackup.c | 12 ++++-----
src/backend/replication/logical/worker.c | 14 +++++-----
src/backend/replication/walreceiver.c | 10 +++----
src/backend/replication/walsender.c | 9 ++++---
src/backend/tcop/pquery.c | 2 ++
src/backend/utils/adt/nabstime.c | 1 +
src/backend/utils/cache/inval.c | 2 ++
src/backend/utils/time/snapmgr.c | 45 ++++++++++++++++---------------
src/bin/pg_basebackup/pg_recvlogical.c | 18 ++++++-------
src/bin/pg_basebackup/receivelog.c | 22 +++++++--------
src/bin/pg_basebackup/streamutil.c | 20 +++++++-------
src/bin/pg_basebackup/streamutil.h | 7 ++---
src/include/datatype/timestamp.h | 4 ---
src/include/utils/snapmgr.h | 7 ++---
src/include/utils/snapshot.h | 3 ++-
src/include/utils/timestamp.h | 7 -----
22 files changed, 100 insertions(+), 94 deletions(-)