Address soundness of IR optimizations

[aslanix]

At the moment, IR optimizations are disabled, because they introduce semantic bugs that change failure behavior of the programs – programs that fail without optimizations may succeed with them. The example is test seqcomp_neg01.trp. Without optimizations, this program has a type error in addition. The optimization removes the 1+ section of the code, deeming it an unused declaration, which results in failure-free execution.