[FIX] structures: Revert r48396 - second attempt at checking perms for navigation buttons in structures (skipping over interleaved "hidden" pages).
Works for next, prev & parent arrows also but not "home".

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@48406 b456876b-0849-0410-b77d-98878d47e9d5