Post-codegen mutual exclusion analysis

[grebe]

Post-codegen analysis may be needed to determine if channel operations are mutually exclusive. This may be because mutual exclusion is somehow data dependent in a way that can be determined only when a leaf block is integrated into the larger design context, or it may be because the proof is expensive and should be done out of band.

Regardless of the reason, it's useful to be able to do analysis after codegen. If multi-proc codegen is supported, an alternative channel adapter implementation can be substituted after codegen.