[PATCH] Add a fallback mechanism for undefined atom.

[Shankar Kalpathi Easwaran]

  The problem is this functionality can be used and latercould break tests in the future when the real functionality is implemented.

  It would be difficult later to figure out all dark corners of the code when the aliasing feature is implemented.

  This still needs changes in the Native file format and YAML as Bigcheese suggested.

http://llvm-reviews.chandlerc.com/D1550