test serialization/deserialization of clang IR with new checked types and new bounds expressions

[secure-sw-dev-bot]

This issue was copied from checkedc/checkedc-clang#3

---

We added code for serializing and deserializing clang IR with the new checked types. This is necessary to get the code to compile. However, the serialization and deserialization of IR with these types has no tests. We should add tests before people start using compiler functionality that depends on this.