Optimize GenBCode: dealiasWiden rather than normalize
Dealias, rather than normalize in Uncurry's info transformer

And compensate in Erasure by flattening refined types before
synthesizing compound isInstanceOf checks.
Optimization in Pickler

Avoid creating an intermediate array.

The pickling phase takes about 2% of compilation; writeArray was
reporting 30% of this, and the call to take about 25% of that.

A microoptimization at best. But, life is a game of inches.
Optimize GenSeqLike.equals

Fast path if this and that are the same reference. This
is important in LazyTreeCopier; time spent in List.sameElements
drops from 1000ms to 440ms in a 150s compiler run.