pgsql: Fix getDatumCopy(): don't use store_att_byval to copy into a

Log Message:
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Fix getDatumCopy(): don't use store_att_byval to copy into a Datum
variable (this accounts for regression failures on PPC64, and in fact
won't work on any big-endian machine). Get rid of hardwired knowledge
about datum size rules; make it look just like datumCopy().

Modified Files:
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pgsql/src/backend/access/gin:
ginbulk.c (r1.3 -> r1.4)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gin/ginbulk.c.diff?r1=1.3&r2=1.4)