pgsql: Hmm, seems --disable-spinlocks has been broken for awhile and

Log Message:
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Hmm, seems --disable-spinlocks has been broken for awhile and nobody
noticed.  Fix SpinlockSemas() to report the correct count considering
that PG 8.1 adds a spinlock to each shared-buffer header.

Tags:
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REL8_1_STABLE

Modified Files:
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    pgsql/src/backend/storage/lmgr:
        spin.c (r1.17.2.1 -> r1.17.2.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/lmgr/spin.c.diff?r1=1.17.2.1&r2=1.17.2.2)