[PATCH] cpp11-migrate: Write header replacements to disk

[Edwin Vane]

  I'm thinking something like this:
  ```
  filename: file.h
  Transforms:
    - ID: UseAuto
      Replacements:
        - Offset: 5
          Length: 10
          ReplacementText: "Hello!"
        - Offset: 20
          Length: 2
          ReplacementText: "Goodbye!"
    - ID: AddOverride
      Replacements:
        - Offset: 10
          Length: 10
          ReplacementText: "urgh!!"
  ```

http://llvm-reviews.chandlerc.com/D1142