task! can be re-added in a backward compatible fashion and I'd like to not have
two ways to assign a task handler to an interrupt / exception in the first
release.
rtfm::atomic now uses the `Threshold` token instead of the `CriticalSection`
token. This reduces overhead by dropping the "are interrupts enabled?" check.
- allow trailing commas in list of resources
- make task.resources optional
- add rtfm::set_pending function which can be used to force an interrupt into
the pending state. This is a replacement of the old rtfm::request.
rtfm::set_pending takes the Interrupt enum provided by the device crate as
argument. (The old rtfm::request took a task function as argument)
- the user may want to use types they imported into the root of the crate. These
types are not available in e.g. `mod idle` so `idle::Resources` *can't* be
defined in that module. To workaround this problem `idle::Resources` will be
defined in the root, with some other name, and then be re-exported in the
`idle` module.
- remove the "a resource only used by one task should be local data" check. In
some cases you do want a resource owned by a single task instead of local
data since `init` can access resources but not a task local data.
