syntax tweaks, relax check, add set_pending(), deal with imported types

- 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.

src/lib.rs

@@ -12,6 +12,7 @@ pub use cortex_m::asm::{bkpt, wfi};
 pub use cortex_m::interrupt::CriticalSection;
 pub use cortex_m::interrupt::free as atomic;
 pub use static_ref::Static;
+use cortex_m::interrupt::Nr;
 #[cfg(not(armv6m))]
 use cortex_m::register::{basepri_max, basepri};
 
@@ -175,6 +176,16 @@ impl Threshold {
 
 impl !Send for Threshold {}
 
+/// Sets an interrupt as pending
+pub fn set_pending<I>(interrupt: I)
+where
+    I: Nr,
+{
+    // NOTE(safe) atomic write
+    let nvic = unsafe { &*cortex_m::peripheral::NVIC.get() };
+    nvic.set_pending(interrupt);
+}
+
 #[macro_export]
 macro_rules! task {
     ($NAME:ident, $body:path) => {