Portal map search:
  - more IE8 fixes (minor js optimisation)
  - IE8 special-purpose warning notice on map view
  - for IE8 AJAX callback (search/filter), we used to restrict
    rows to 500. However, that had the unintended side-effect of
    limiting non-map searches to 500 rows: something that royally
    screws up normal searches (which have 10 rows). Soo... we still
    retrieve all searches for map view in IE8, but only operate on
    the first 500 matches. This required a bit of fiddling about,
    but at least now normal searching isn't adversely impacted