plpsm - plpgpsm: merge patch: Fix up plpgsql's "simple expression"

Log Message:
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merge patch: Fix up plpgsql's "simple expression" evaluation mechanism so that

Modified Files:
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plpgpsm/src:
pl_exec.c (r1.28 -> r1.29)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plpsm/plpgpsm/src/pl_exec.c.diff?r1=1.28&r2=1.29)
pl_handler.c (r1.1.1.1 -> r1.2)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plpsm/plpgpsm/src/pl_handler.c.diff?r1=1.1.1.1&r2=1.2)
plpgpsm.h (r1.20 -> r1.21)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plpsm/plpgpsm/src/plpgpsm.h.diff?r1=1.20&r2=1.21)