ModularBigInteger does not override hashCode (but overrides equals)

[iaik-jheher]

ModularBigInteger overrides equals, but does not override hashCode.
Thus, distinct objects that compare equally (using structural equality) will not have the same hashCode.

This violates the general hashCode contract.

MWE:

val creator = ModularBigInteger.creatorForModulo(7)
val a = creator.fromInt(6)
val b = creator.fromInt(6)

if (a == b) {
  require(a.hashCode() == b.hashCode())
}