Fix portability issues with the Capsicum patch committed in r339216:
- Wrap access to pw_change and pw_expire in the appropriate #ifdefs.
- Wrap calls to login_cap(3) API in appropriate #ifdefs.
- Add wrapper for transferring time_t, which is still only 32 bits wide on FreeBSD i386.
- Use a temporary variable to deserialize size_t.
Approved by: re (gjb)