pgsql: Put back adjust_appendrel_attrs()'s code for dealing with

Log Message:
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Put back adjust_appendrel_attrs()'s code for dealing with RestrictInfo.
I mistakenly removed it last month, thinking it was no longer needed ---
but it is still needed for dealing with joininfo lists. Fortunately this
bit of brain fade hadn't made it into any released versions yet.

Tags:
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REL8_4_STABLE

Modified Files:
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pgsql/src/backend/optimizer/prep:
prepunion.c (r1.171.2.1 -> r1.171.2.2)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/prep/prepunion.c?r1=1.171.2.1&r2=1.171.2.2)