pgsql: Use ShmemInitStruct to allocate shmem for semaphores

Use ShmemInitStruct to allocate shmem for semaphores

This makes them visible in pg_shmem_allocations

Reviewed-by: Tomas Vondra <tomas@vondra.me>
Discussion: https://www.postgresql.org/message-id/01ab1d41-3eda-4705-8bbd-af898f5007f1@iki.fi

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/40c41dc77306bf6f8f97b0012355c0dd8e11a430

Modified Files
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src/backend/port/posix_sema.c | 4 +++-
src/backend/port/sysv_sema.c  | 5 ++++-
2 files changed, 7 insertions(+), 2 deletions(-)