[VCLLVM] Add partial contract support for LLVM

[Drevanoorschot]

This PR adds function contract support for LLVM programs. It's not entirely finished and there are still some issues. However, it compiles and to prevent future merge conflicts, I felt like it would be best to create this PR anyway.

Some of the issues/notes:

• When using the \result keyword, the AmbigiousResult.ref reference is never set. I'm not sure why this is or where the reference assignment is supposed to happen either.
• Since parsing the contract is delayed until one of the rewrite steps. The build definitions had to be altered slightly. Most notably it includes making parsers a dependency of rewrite.

[Drevanoorschot]

Latest commit on the branch solves both these issues:

• When using the \result keyword, the AmbigiousResult.ref reference is never set. I'm not sure why this is or where the reference assignment is supposed to happen either.

We now make sure the parsed contracts are also passed through the resolver by making the the contract parsing part of the resolver.

• Since parsing the contract is delayed until one of the rewrite steps. The build definitions had to be altered slightly. Most notably it includes making parsers a dependency of rewrite.

Since the resolver is part of the col module, the rewrite module does not depend on the parser module anymore. This change has also been reflected in the build definition

[Drevanoorschot]

It would be nice if you could take this out now that we decided we should do parsing from resolution: it is also consistent with the notion that there should be no logic or unexpected stuff in the antlr -> col transformatiosn.

Latest commit should resolve above issue. I'm planning to implement invocations in contracts soon too. Since it's kind of related I could add to this PR or open a separate PR for it.

[pieter-bos]

@Drevanoorschot What's the state of this now, should this be merged?

[Drevanoorschot]

Yes, this branch can be merged. Apologies for not having been clear about the status of this PR