python - be: Actually identify the resultinfo node as ReturnSetInfo, and

Log Message:
-----------
Actually identify the resultinfo node as ReturnSetInfo, and use
ecxt_per_query_memory for VPC SRF returns.(?)

Modified Files:
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be/src:
pl.c (r1.16 -> r1.17)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/pl.c.diff?r1=1.16&r2=1.17)