k20::{sim, pin}: Port to ioregs!
k20::uart: Port to ioregs!
k20::sim: Export regs
k20::uart: Make UART naming consistent with documentation
k20::uart: Enable transmission/reception in set_mode
Merge pull request #129 from bgamari/ioreg-k20

Refactor K20 to use ioreg!
Merge pull request #192 from bgamari/misc

Various fixes
util::shared: Fix nightly churn
util::shared: Allow dead code for NoInterrupts
util::shared: Always compile

This really isn't specific to multitasking
os::cond_var: Dust off and add single-threaded implementation
os::cond_var: Always compile
cortex: Move NoInterrupts to common
mutex: Style fixes
mutex: Single threaded implementation
mutex: Always compile
Merge pull request #194 from bgamari/concurrency

Concurrency  primitives
lang_items: Silence unused argument warning
k20::sim: Fix non-snake-case warning
drivers::chario: Kill unused use