message: [zPIV] Fix bignum overloads when using OpenSSL
  Similar to the `CBigNum()` overloads when using GMP, there is no need to
  use special pre-compiler logic for `__APPLE__`'s int64_t; just use
  `long long`.
diff: @@ -98,14 +98,12 @@ public:
  CBigNum(short n) { bn = BN_new(); if (n >= 0) setulong(n); else setint64(n); }
  CBigNum(int n) { bn = BN_new(); if (n >= 0) setulong(n); else setint64(n); }
  CBigNum(long n) { bn = BN_new(); if (n >= 0) setulong(n); else setint64(n); }
  -#ifdef __APPLE__
  - CBigNum(int64_t n) { bn = BN_new(); setint64(n); }
  -#endif
  + CBigNum(long long n) { bn = BN_new(); setint64(n); }
  CBigNum(unsigned char n) { bn = BN_new(); setulong(n); }
  CBigNum(unsigned short n) { bn = BN_new(); setulong(n); }
  CBigNum(unsigned int n) { bn = BN_new(); setulong(n); }
  CBigNum(unsigned long n) { bn = BN_new(); setulong(n); }
  - // CBigNum(uint64_t n) { bn = BN_new(); setuint64(n); }
  + CBigNum(unsigned long long n) { bn = BN_new(); setuint64(n); }
  explicit CBigNum(uint256 n) { bn = BN_new(); setuint256(n); }
  explicit CBigNum(const std::vector<unsigned char>& vch)
  