Fix minor bugs

...janne/libquassel/client/session/ClientHandshakeHandler.kt

...libquassel/protocol/serializers/qt/QDateTimeSerializer.kt

...tocol/serializers/signalproxy/HeartBeatReplySerializer.kt

...el/protocol/serializers/signalproxy/InitDataSerializer.kt

...anne/libquassel/protocol/syncables/common/BufferSyncer.kt

...justjanne/libquassel/protocol/syncables/common/IrcUser.kt

...tlin/de/justjanne/libquassel/protocol/variant/QVariant.kt

...n/de/justjanne/libquassel/protocol/variant/QVariantMap.kt

...rotocol/serializers/signalproxy/InitDataSerializerTest.kt

...justjanne/libquassel/protocol/syncables/IrcChannelTest.kt

.../libquassel/protocol/testutil/matchers/TemporalMatcher.kt

...tjanne/libquassel/protocol/testutil/mocks/EmptySession.kt