pginstaller - pginst: Add upgrade script and instructions.

Log Message:
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Add upgrade script and instructions.

Modified Files:
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pginst:
README (r1.13 -> r1.14)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pginstaller/pginst/README.diff?r1=1.13&r2=1.14)

Added Files:
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pginst/package:
README (r1.2)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pginstaller/pginst/package/README?rev=1.2&content-type=text/x-cvsweb-markup)