make the ceiling part of the task signature

src/lib.rs

tests/cfail/access.rs

tests/cfail/ceiling.rs

tests/cfail/lock.rs

tests/cfail/peripherals-alias-2.rs

tests/cfail/race-1.rs

tests/cfail/race-2.rs

tests/cfail/tasks-p0.rs

tests/cfail/tasks-same-handler.rs

tests/cfail/tasks-wrong-ceiling.rs

tests/cfail/tasks-wrong-idle.rs

tests/cfail/tasks-wrong-init.rs

tests/cfail/tasks-wrong-priority.rs

tests/cfail/tasks-wrong-task.rs