This patch creates theme_l() that can be overriden by themes. The original l() stays, because it is used for 'administrative' actions. The patch doesn't work yet, since for some reason theme('l'); doesn't actually call theme_l(). I need to look into this problem a little closer, but perhaps somebody can give me a nudge in the right direction.
Passed: 14674 passes, 0 fails, 0 exceptions
Passed: 14694 passes, 0 fails, 0 exceptions
Failed: 14652 passes, 0 fails, 1 exception
Failed: 14618 passes, 0 fails, 1 exception
Failed: 14681 passes, 0 fails, 1 exception