…ysis

The analyzer is parameterized by an abstract domain and a transfer function.

For recursive handlers, it remembers the latest inferred abstract state
and uses it to start the next fixpoint iteration.  This avoids behaviors
exponential in the nesting of recursive handlers, like we would have
if we started every iteration with bottom.

This exponential behavior was present in the old implementation of liveness
analysis.  It is gone in the new implementation that just calls into
the generic analyzer.