Prepare for the android UI module

* Not all pthreads features are supported on Android, thus the changes.
* Changing the `data_store` signature is enough to support nulls because the APIs of both underlying implementations already supported them.
* Declaring the lines for <activity> in the modules allows for non-fullscreen and non-orientation-locked apps!
Ne pas faire de retour si le thread "va être cancellé" ou "a été cancellé"?