Refactor: Reduce code duplication within the platform specific event handling.

Signed-off-by: Janne Hakonen <janne.hakonen@oss.tieto.com>
Move event handling to new class FreeRdpEventLoop. Renamed EventProcessor to FreeRdpClient.

Signed-off-by: Janne Hakonen <janne.hakonen@oss.tieto.com>
Add mouse handling.

Signed-off-by: Janne Hakonen <janne.hakonen@oss.tieto.com>