Fix problem with expiration dates after 2038 on 32-bit systems
Interpret the expiration time of a subkey as unsigned 32-bit value (as
gpg does internally) and store time values as qint64 values.
(cherry picked from commit 40b52f117053dea86ae9e42b26e7124b5f8b8b96)
- GnuPG-bug-id: T7069