plscheme - plscheme: Fixed an important bug about NULL handling when

Log Message:
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Fixed an important bug about NULL handling when returning nested records. (And
some other minor fixes related with NULL issues.)

Added SRF functionality. (Using materialize mode instead of value-per-call. See
related comment lines in the handle_func_res() body.)

Modified Files:
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plscheme:
plscheme.c (r1.12 -> r1.13)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plscheme/plscheme/plscheme.c.diff?r1=1.12&r2=1.13)