pgsql: Remove --disable-spinlocks.

Remove --disable-spinlocks.

A later change will require atomic support, so it wouldn't make sense
for a hypothetical new system not to be able to implement spinlocks.

Reviewed-by: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> (concept, not the patch)
Reviewed-by: Andres Freund <andres(at)anarazel(dot)de> (concept, not the patch)
Discussion: https://postgr.es/m/3351991.1697728588%40sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/e25626677f8076eb3ce94586136c5464ee154381

Modified Files
--------------
configure | 40 -------
configure.ac | 13 ---
doc/src/sgml/installation.sgml | 37 +------
meson.build | 6 --
src/backend/port/atomics.c | 26 -----
src/backend/port/posix_sema.c | 3 +-
src/backend/port/sysv_sema.c | 3 +-
src/backend/postmaster/launch_backend.c | 8 --
src/backend/storage/ipc/ipci.c | 10 --
src/backend/storage/lmgr/Makefile | 1 -
src/backend/storage/lmgr/meson.build | 1 -
src/backend/storage/lmgr/s_lock.c | 2 +-
src/backend/storage/lmgr/spin.c | 180 --------------------------------
src/include/pg_config.h.in | 3 -
src/include/pg_config_manual.h | 15 ---
src/include/port/atomics.h | 4 +-
src/include/port/atomics/fallback.h | 4 +-
src/include/storage/s_lock.h | 39 +------
src/include/storage/spin.h | 18 +---
src/test/regress/regress.c | 86 ---------------
20 files changed, 13 insertions(+), 486 deletions(-)