pgsql: Replace use of strerror() with %s by %m in pg_waldump

Replace use of strerror() with %s by %m in pg_waldump

Since d6c55de1, src/port/snprintf.c is able to use %m instead of
strerror(). A couple of utilities in src/bin/ have already done the
switch, and do it now for pg_waldump as this reduces the workload for
translators.

Note that more could be done, particularly with pgbench. Thanks to
Kyotaro Horiguchi for the discussion.

Discussion: https://postgr.es/m/20191129065115.GM2505@paquier.xyz

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/cce64a51cabc1e59d202d95bb0b92ed22bac73cf

Modified Files
--------------
src/bin/pg_waldump/pg_waldump.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)