[PATCH] [analyzer] Refactor conditional expression evaluating code

[Pavel Labath]

  I have added a couple more tests to D1259 with ternary and nested expressions, and they seem to work fine. The reason I don't need to handle non-directly nested expressions specially is that if a child of a conditional operator is anything else than an another conditional operator, it's value will be computed in the normal way and added to the environment. Conditional operators were the only problem, as they didn't store their values in the environment, but only "stored" them implicitly, in the structure of the CFG. This was possible because VisitLogicalExpr reconstructed the value by digging in the ExplodedGraph history. I wanted to store the values explicitly, because I will need them later, and the topmost logical expression seemed like the best place to do that, since it has access to all of the sub-expressions and is the point where all the CFG paths converge.

  PS: I did not add any new tests to this patch specifically, as this does not introduce any new features, and I am hoping that conditional expressions are covered enough already. If you think it's necessary, and can add a couple more here as well.

http://llvm-reviews.chandlerc.com/D1340