pgsql: All POSIX systems have langinfo.h and CODESET.

All POSIX systems have langinfo.h and CODESET.

We don't need configure probes for HAVE_LANGINFO_H (it is implied by
!WIN32), and we don't need to consider systems that have it but don't
define CODESET (that was for OpenBSD in commit 81cca218, but it has now
had it for 19 years).

Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Discussion: https://postgr.es/m/CA%2BhUKGJqVe0%2BPv9dvC9dSums_PXxGo9SWcxYAMBguWJUGbWz-A%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/14c648ff009438830d15de7c8a93c2b29114eb1c

Modified Files
--------------
configure                       |  2 +-
configure.ac                    |  1 -
meson.build                     |  1 -
src/bin/pg_upgrade/pg_upgrade.c |  4 ----
src/include/pg_config.h.in      |  3 ---
src/port/chklocale.c            | 20 +-------------------
6 files changed, 2 insertions(+), 29 deletions(-)