Consumed analysis: add two new attributes which fine-tune the behavior of
consumable objects.  These are useful for implementing error codes that
must be checked.  Patch also includes some significant refactoring, which was
necesary to implement the new behavior.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199169 91177308-0d34-0410-b5e6-96231b3b80d8