pgsql: Install a hopefully-temporary workaround for Snow Leopard

Log Message:
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Install a hopefully-temporary workaround for Snow Leopard readdir() bug.
If Apple doesn't fix that reasonably soon, we'll have to consider
back-patching a workaround; but for now, just hack it in HEAD so that
we can get buildfarm reports on HEAD from OS X machines.
Per Jan Otto.

Modified Files:
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pgsql/src/backend/commands:
tablespace.c (r1.61 -> r1.62)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablespace.c?r1=1.61&r2=1.62)