Bail as early as possible

  Instead of waiting for the domain construction to finish we will now
  bail as early as possible in case a complexity problem is encountered.
  This might save compile time but more importantly it makes the "abort"
  explicit. While we can always check if we invalidated the assumed
  context we can simply propagate the result of the construction back.
  This also removes the HasComplexCFG flag that was used for the very
  same reason.

Differential Revision: http://reviews.llvm.org/D18504

llvm-svn: 264775