Pre-SIP: using underscores for type lambdas

I have already argued that, and I feel very strongly that we’re taking a very dangerous approach. Move slowly and iterate - #33 by curoli

Martin Odersky’s response, IIUC, was basically that the large changes are essential and the ones that could be separated are small anyway. This doesn’t satisfy me but I haven’t taken the time to respond yet. Feel free to chime in on that thread.