pgsql: Remove obsolete platforms from ps_status.c.

Remove obsolete platforms from ps_status.c.

Time to remove various code, comments and configure/meson probes
relating to ancient BSD, SunOS, GNU/Hurd, IRIX, NeXT and Unixware.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CA%2BhUKGJMNGUAqf27WbckYFrM-Mavy0RKJvocfJU%3DJ2XcAZyv%2Bw%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d2ea2d310dfdc40328aca5b6c52225de78432e01

Modified Files
--------------
configure                          | 35 ------------------------
configure.ac                       | 13 ---------
meson.build                        | 17 ------------
src/backend/utils/misc/ps_status.c | 55 +++++++-------------------------------
src/include/pg_config.h.in         |  3 ---
src/tools/msvc/Solution.pm         |  1 -
6 files changed, 9 insertions(+), 115 deletions(-)