pginstaller - web: Add mention of multiprocess architecture Add

Log Message:
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Add mention of multiprocess architecture
Add workaround for no-privs-to-install-service on upgrade

Modified Files:
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web/faq:
FAQ_windows.html (r1.4 -> r1.5)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pginstaller/web/faq/FAQ_windows.html.diff?r1=1.4&r2=1.5)