OpenSSL::PKey::EC::Point#invert!

static VALUE ossl_ec_point_invert(VALUE self)
{
    EC_POINT *point;
    const EC_GROUP *group;

    GetECPoint(self, point);
    GetECPointGroup(self, group);

    if (EC_POINT_invert(group, point, ossl_bn_ctx) != 1)
        ossl_raise(eEC_POINT, "EC_POINT_invert");

    return self;
}