pgsql: Fix ALTER COLUMN TYPE bug: it sometimes tried to drop UNIQUE or

Log Message:
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Fix ALTER COLUMN TYPE bug: it sometimes tried to drop UNIQUE or PRIMARY KEY
constraints before FOREIGN KEY constraints that depended on them.  Originally
reported by Neil Conway on 29-Jun-2005.  Patch by Nakano Yoshihisa.

Tags:
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REL8_0_STABLE

Modified Files:
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    pgsql/src/backend/commands:
        tablecmds.c (r1.142.4.4 -> r1.142.4.5)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c.diff?r1=1.142.4.4&r2=1.142.4.5)