2.2.0

Added:

• Added Element::coefficients() and Element::rationalCoefficients() for
  the deprecated Element::coefficients<C>().

• Explicit overloads of Element::operator*= and Element::operator/= for
  mpz_class and mpq_class since the old template-based approach is not
  supported when building on clang with -fvisibility=hidden.

Deprecated:

• Deprecated Element::coefficients<C>(). The method is not visible when
  building with clang and fvisibility=hidden, coefficients() and
  rationalCoefficients() should be used instead.

Fixed:

• Printing of elements when compiling with clang.