Version 0.4.2.1

This version of libQMatrixClient contains a single fix: the library no more treats fake state events (that don't have state_key, even if they have state-related type, e.g., m.room.topic) as state events, turning them into unknown events instead. It is strongly recommended to upgrade from any 0.4.x version to 0.4.2.
(Update: version 0.4.2 had still the old version number in its CMakeLists.txt; version 0.4.2.1 has the version number correctly updated.)