Implement an analysis to identify no-return functions

[travitch]

A no-return function is a function that, when called, can never return. It is useful for macaw to know about these functions so that it can avoid analyzing code after a call to a no-return function, which is actually junk that can never be executed. Currently, macaw enables users to manually identify such functions through the trustedFunctionEntryPoints field of the DiscoveryState. This manual specification works, but is cumbersome.

It would be ideal if macaw could identify these functions automatically. This could be accomplished with a bottom-up analysis of discovered functions to determine which ones call exit, abort, or issue a similar system call. Note that there might need to be a mode to turn the analysis off in the rare cases where the exit symbol does not correspond to the C library version.

This would depend on the work in #298, which would enable functions that call no-return functions to be re-analyzed with the new information, refining the results.

Note that this could live in macaw-base, but might be better-suited to macaw-refinement as an additional heuristic.