Simplify Mul.as_real_imag() for imaginary multiplicands (issue 3329)
Fix failing diff test after Mul.as_real_imag() modifications (issue 3329)
Merge pull request #2042 from skirpichev/3329-mul-as_real_imag

Simplify Mul.as_real_imag() for imaginary multiplicands (issue 3329)