troubleshooting menu_scroller

Added function is_portfolio_currently_displayed to provide quick,
consistent test for if 'le_portfolio' or 'homepage' DIVs are currently
displayed.  Returns TRUE on for portfolio DIV.

 Chrome fix: added is_portfolio_currently_displayed test to scroller
function to trigger hide_portfolio if currently displayed, and to add a
timeout on scroll event to allow for transition.

Variable this_portfolio_passer used to resolve scope issue with timeout.

Timeout set to zero when 'homepage' DIV currently visible
(is_portfolio_currently_displayed == FALSE)

Working on determining why scroller doesn't work at all in Firefox.