implement RFCs 147 and 155, etc.

This commit:

- Implements RFC 147: "all functions must be safe"

- Implements RFC 155: "explicit Context parameter"

- Implements the pending breaking change #141: reject assign syntax in `init`
  (which was used to initialize late resources)

- Refactors code generation to make it more readable -- there are no more random
  identifiers in the output -- and align it with the book description of RTFM
  internals.

- Makes the framework hard depend on `core::mem::MaybeUninit` and thus will
  require nightly until that API is stabilized.

- Fixes a ceiling analysis bug where the priority of the system timer was not
  considered in the analysis.

- Shrinks the size of all the internal queues by turning `AtomicUsize` indices
  into `AtomicU8`s.

- Removes the integration with `owned_singleton`.

Cargo.toml

@@ -12,7 +12,7 @@ license = "MIT OR Apache-2.0"
 name = "cortex-m-rtfm"
 readme = "README.md"
 repository = "https://github.com/japaric/cortex-m-rtfm"
-version = "0.4.3"
+version = "0.5.0-alpha.1"
 
 [lib]
 name = "rtfm"
@@ -36,12 +36,13 @@ required-features = ["timer-queue"]
 [dependencies]
 cortex-m = "0.5.8"
 cortex-m-rt = "0.6.7"
-cortex-m-rtfm-macros = { path = "macros", version = "0.4.3" }
-heapless = "0.4.1"
-owned-singleton = "0.1.0"
+cortex-m-rtfm-macros = { path = "macros", version = "0.5.0-alpha.1" }
+
+[dependencies.heapless]
+features = ["smaller-atomics"]
+version = "0.4.1"
 
 [dev-dependencies]
-alloc-singleton = "0.1.0"
 cortex-m-semihosting = "0.3.2"
 lm3s6965 = "0.1.3"
 panic-halt = "0.2.0"