qt: Allow retrieving the default value of a config entry
* lang/qt/src/cryptoconfig.cpp, lang/qt/src/cryptoconfig.h (CryptoConfigEntry::defaultValue): New. * lang/qt/src/qgpgmenewcryptoconfig.cpp, lang/qt/src/qgpgmenewcryptoconfig.h (QGpgMENewCryptoConfigEntry::defaultValue): New. * lang/qt/tests/t-config.cpp (CryptoConfigTest::testDefault()): Add test of CryptoConfigEntry::defaultValue(). Port away from deprecated CryptoConfig::entry overload.
- GnuPG-bug-id: T5515