pgsql: Reduce the default size of the local lock hash table.

Log Message:
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Reduce the default size of the local lock hash table.  There's usually
no need for it to be nearly as big as the global hash table, and since
it's not in shared memory it can grow if it does need to be bigger.
By reducing the size, we speed up hash_seq_search(), which saves a
significant fraction of subtransaction entry/exit overhead.

Modified Files:
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    pgsql/src/backend/storage/lmgr:
        lock.c (r1.143 -> r1.144)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/lmgr/lock.c.diff?r1=1.143&r2=1.144)