Function rs::layout::seat::handle_release_key

pub fn handle_release_key(
    layout: &mut Layout, 
    submission: &mut Submission, 
    ui: Option<&UIBackend>, 
    time: Timestamp, 
    manager: Option<(&State, Threaded<Application>)>, 
    button_pos: &ButtonPosition
)

Mutates layout and sends events. This split away from handle_release_key in order to pull at least some of the mutation away from what should some day be core functional logic.