plproxy - plproxy: docs: tag all functions with embedded SELECT with

Log Message:
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docs: tag all functions with embedded SELECT with SETOF

Modified Files:
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plproxy/doc:
overview.txt (r1.7 -> r1.8)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plproxy/plproxy/doc/overview.txt.diff?r1=1.7&r2=1.8)
tutorial.txt (r1.3 -> r1.4)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/plproxy/plproxy/doc/tutorial.txt.diff?r1=1.3&r2=1.4)