Worked on SpinLock (INCOMPLETE)

Added basic Spinlock to Korlib.
Added Test instruction to TinySimulator.
Added SpinLock internal intrinsic compiler replacement.
Updated ReplacementTargetAttribute to allow multiple uses.
Fix issue from upstream merge.
Finished implementing SpinLock.

Finished implementing a rudimentary version of SpinLock that does not
follow .NET spec.
Also shifted the PlatformIntrinsicTransformationStage to run after the
IRTransformationStage.