BFMSS

An implementation of "A Separation Bound for Real Algebraic Expressions", by Burnikel, Funke, Mehlhorn, Schirra, and Schmitt. This provides a good ZeroBoundFunction for use in sign tests.

Unlike the paper, we use log-arithmetic instead of working with exact, big integer values. This means our bound isn't technically as good as it could be, but we save the cost of working with arithmetic. We also perform all log arithmetic using Longs and check for overflow (throwing ArithmeticExceptions when detected). In practice we shouldn't hit this limit, but in case we do, we prefer to throw over failing silently.