These utilities are needed for generating the code that supports
summaries; in order to move summary logic into front_end, we will need
these code generation tools in front_end as well.
Also make a minor change to summary code generation logic so that it
talks to the file system directly rather than depending on analyzer's
file system abstraction.
R=brianwilkerson@google.com
Review-Url: https://codereview.chromium.org/2742333005 .
Devon Carew