polyvariant self compile

[Stephen Weeks]

It failed with a stack size of 20m, but completed normally with a
stack size of 40m.  Given a maximum stack frame size of 6440, this
implies a stack depth of at least 3256.  The running time of G1 was
1240s, while the running time of G0 was 2056s, for a ratio 0f 0.6,
which is about the same ratio as without polyvariance.  I.E.,
polyvariance did not seem to help the compiler much.  I'll do a run
now with instrumentation.