[PATCH] Fix crash in CFGReachabilityAnalysis triggered by IdempotentOperationChecker.

[Ted Kremenek]

  IdempotentOperationsChecker has suffered from several known limitations for a while, but the addition of interprocedural analysis has certainly compounded the issues.  I had thought about it at the time when we added interprocedural analysis, but it never became a pressing action item.

  This checker has been in the alpha state for a couple years now.  Making it real is going to take a lot of work beyond just fixing these immediate issues.  I think we should just go and remove it entirely.  If we want to resuscitate it one day we can.

http://llvm-reviews.chandlerc.com/D2427