Inline subroutines

## Summary

It would be a good optimization to identify subroutines that can be inlined directly into the caller code instead of being a legitimate subroutine. A common use case for subroutines is to increase readability, not necessarily because they are called frequently.

## Scope

If a subroutine is only called from one place, it will always be more efficient to inline that subroutine into the caller code.

If a subroutine is called from multiple places, it *might* be more efficient to inline it if it's body is sufficiently small, but this is a more complex case to analyze, and likely less important. I only include it here for completeness--this issue should probably not address it.