- normal() now internally keeps numerator and denominator separated and

- normal() now internally keeps numerator and denominator separated and
  doesn't combine them to a fraction until the very end. All implementations
  of basic::normal() now return a 2-component lst {num, den} instead of a
  simple expression.
- dropped status_flags::normal_form
- ex::numer() and ex::denom() didn't work correctly on numerics
- lcm(a, b) with a and b being a numeric returned the GCD of a and b (*argh*)