How do I make Alt-(x) send Meta-(x)?

[bdonlan]

Portage recently installed x11-terms/xterm-184 over the old built-into-X version. Since then, combinations like Alt-2 have been displaying extended characters (² in the case of Alt-2) instead of sending a meta before the character in question. How do I get the old behavior back? Meta does work properly in rxvt, but rxvt does not seem to support unicode.