highlight helper ignoring special chars support.

Hi,

I've created a patch for highlight helper that ignores accents, ...
this is especially useful when using with search which typically
returns results regardless of special accents. Since most of non-
english speaking countries ) use some sort of accented characters,
this could make its way to core.

More at https://rails.lighthouseapp.com/projects/8994/tickets/3593-patch-support-for-highlighting-with-ignoring-special-chars

Could someone review this? Comments?

johno