Обсуждение: pgsql: Reset btpo.xact following recovery of btree delete page.

Log Message:
-----------
Reset btpo.xact following recovery of btree delete page. Add btpo_xact
field into WAL record and reset it from there, rather than using
FrozenTransactionId which can lead to some corner case bugs.

Problem report and suggested route to a fix from Heikki, details by me.

Modified Files:
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    pgsql/src/backend/access/nbtree:
        nbtpage.c (r1.120 -> r1.121)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtpage.c?r1=1.120&r2=1.121)
        nbtxlog.c (r1.62 -> r1.63)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtxlog.c?r1=1.62&r2=1.63)
    pgsql/src/include/access:
        nbtree.h (r1.130 -> r1.131)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/access/nbtree.h?r1=1.130&r2=1.131)