WIP: Use LHS components as synthesis components

[rsas]

This WIP PR adds a parameter to instruction synthesis corresponding to a vector of instructions from the LHS that can be used as components in synthesis. The instructions are initialized as ordinary library components and are reconstructed if a candidate is found.

The first test case test/Infer/four-adds.opt shows that the synthesis engine can reconstruct the original LHS out of two sub-components (two adds). Feel free to add more reasonable tests.

Usage: LHS components are always initialized. You might want to specify additional components/constants manually using -souper-synthesis-comps=.... Otherwise, the whole component library will be initialized as well (slow).

You will probably encounter issues, please provide me test cases, thanks!

[googlebot]

So there's good news and bad news.

👍 The good news is that everyone that needs to sign a CLA (the pull request submitter and all commit authors) have done so. Everything is all good there.

😕 The bad news is that it appears that one or more commits were authored or co-authored by someone other than the pull request submitter. We need to confirm that all authors are ok with their commits being contributed to this project. Please have them confirm that here in the pull request.

Note to project maintainer: This is a terminal state, meaning the cla/google commit status will not change from this state. It's up to you to confirm consent of the commit author(s) and merge this pull request when appropriate.

[googlebot]

CLAs look good, thanks!

[regehr]

why does stupid googlebot keep complaining

[regehr]

this is awesome! I have a long drive home tomorrow and will try this out / write tests when I get there

[rsas]

@regehr The googlebot complaint is valid, I initially started with a merge from your branch, then squashed leaving you as a committer. I change it to me, looks good now.