pgsql: Fix new warnings from GCC 7

Fix new warnings from GCC 7

This addresses the new warning types -Wformat-truncation
-Wformat-overflow that are part of -Wall, via -Wformat, in GCC 7.

Branch
------
REL9_6_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/47b4913050a320bfba55fa65d52d9ba15488bc70

Modified Files
--------------
contrib/pg_standby/pg_standby.c | 6 +++---
src/backend/access/heap/rewriteheap.c | 4 ++--
src/backend/access/transam/xlog.c | 6 +++---
src/backend/postmaster/pgstat.c | 4 ++--
src/backend/replication/basebackup.c | 4 ++--
src/backend/replication/logical/reorderbuffer.c | 2 +-
src/backend/replication/logical/snapbuild.c | 4 ++--
src/backend/replication/slot.c | 6 +++---
src/backend/storage/file/copydir.c | 10 +++++-----
src/backend/storage/file/fd.c | 12 ++++++------
src/backend/storage/file/reinit.c | 8 ++++----
src/backend/storage/ipc/dsm.c | 4 ++--
src/backend/utils/adt/dbsize.c | 14 +++++++-------
src/backend/utils/cache/relcache.c | 4 ++--
src/backend/utils/error/elog.c | 2 +-
src/backend/utils/time/snapmgr.c | 4 ++--
src/bin/initdb/initdb.c | 4 ++--
src/bin/pg_archivecleanup/pg_archivecleanup.c | 4 ++--
src/bin/pg_basebackup/pg_receivexlog.c | 2 +-
src/bin/pg_resetxlog/pg_resetxlog.c | 12 ++++++------
src/bin/pg_rewind/copy_fetch.c | 10 +++++-----
src/timezone/pgtz.c | 4 ++--
22 files changed, 65 insertions(+), 65 deletions(-)