Restored original experimental CAtomicBoolean.
Rewrote CAtomicBoolean based on CAtomic.
Rewrote CAtomicFixnum based on CAtomic.
Updated CAtomicFixnum to use long long. Added max/min constants.
Updated Yardoc for CAtomicBoolean and CAtomicFixnum.
Updated CAtomic method aliases to be true aliases.
Added explicit require statement.
Fixed broken spec when AtomicFixnum extends CAtomicFixnum.
Updated Yardoc for CAtomic
Added simple benchmarks for Atomic, AtomicBoolean, and AtomicFixnum.
Fixed broken compile on 1.9.3 due to missing rb_check_arity (added in 2.0.0).
Trying again to fix the broken 1.9.3 compile.
Merge pull request #130 from ruby-concurrency/refactor/native-atomics

CAtomicBoolean and CAtomicFixnum