[PATCH] Refactor parseFile API to use LinkerInput directly

[Shankar Kalpathi Easwaran]

  I want to leave it the way it was, these are the reasons :-

  1) LinkerInput needs to be light weight
  2) There would be classes that would be derived from LinkerInput, which makes it more harder to accomodate other features(Example : Group would resemble a linker input in the future).

http://llvm-reviews.chandlerc.com/D1598