pgsql: Tidy up claimed supported CPUs and OSes.

Tidy up claimed supported CPUs and OSes.

* Remove arbitrary mention of certain endianness and bitness variants;
it's enough to say that applicable variants are expected to work.
* List RISC-V (known to work, being tested).
* List SuperH and M88K (code exists, unknown status, like M68K).
* De-list VAX and remove code (known not to work).
* Remove stray trace of Alpha (support was removed years ago).
* List illumos, DragonFlyBSD (known to work, being tested).
* No need to single Windows out by listing a specific version, when we
don't do that for other OSes; it's enough to say that we support
current versions of the listed OSes (when 16 ships, that'll be
Windows 10+).

Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Reviewed-by: Greg Stark <stark(at)mit(dot)edu>
Discussion: https://postgr.es/m/CA%2BhUKGKk7NZO1UnJM0PyixcZPpCGqjBXW_0bzFZpJBGAf84XKg%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/92d70b77ebb45ec43c163d7ebfe7a3c613c24621

Modified Files
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contrib/pgcrypto/crypt-blowfish.c | 2 +-
doc/src/sgml/installation.sgml | 13 +++++++------
src/include/storage/s_lock.h | 30 ------------------------------
3 files changed, 8 insertions(+), 37 deletions(-)