pgsql: Seems that the childXids list would be better based on Oid lists

Log Message:
-----------
Seems that the childXids list would be better based on Oid lists than
integer lists.

Modified Files:
--------------
pgsql/src/backend/access/transam:
xact.c (r1.213 -> r1.214)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xact.c.diff?r1=1.213&r2=1.214)