[FIX][bp/r52330][bp/r52752] Check if behind a Frontend-Proxie/Load-Balancer which rewrites ports (some cloud offerings need this) (thanks Soulou)

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/13.x@52753 b456876b-0849-0410-b77d-98878d47e9d5