This adds icons next to links that don't lead to normal HTML documents. For example a link leading to a PDF will display a PDF logo, and a mailto link will display a mail icon.
The code is mostly copied from Wikipedia and also uses the same icons that Wikipedia uses.
Supported audio extensions:
ogg, mid, midi, mp3, wav, wma, ra, m4a, ape, asf, flac, speex, aac
Supported video extensions:
ogm, avi, mpeg, mpg, mkv, mov, wmv, flv, rm, divx, xvid, m4v, mp4
Supported document extensions:
doc, odt, rtf, docx, xls, ods, odp, ppt, pps, pdf
Supported protocols:
mailto:, ftp://, irc://