Fix rounding bug in bsqrt() in Math::BigInt. Also make bsqrt() upgrade only
when necessary.Simplify and speed up bsqrt() (for computing the square root) in
Math::BigFloat. The computation time now mainly depends on the desired
accuracy, not the number of digits in the significand.Add support for using "div_scale" as import parameter, like this
use Math::BigFloat div_scale => 80;
Add better argument checking when the "div_scale" value is set by the
user.