re-organize include dir: app/ subdir?

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on August 22, 2014 17:31:46_

With the addition of the annotation headers (3 for app, 1 for client) we may want to add some heirarchy to the include/ dir. One suggestion is to have the 3 app annotation headers (currently in include/annotations/) and dr_app.h together in include/app/.

We may also want to rename dr_annotation.h vs dr_annotations.h?

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=1524_

Start by reviewing the headers in include/annotations/ and dr_app.h, then search the repository for references to their current paths and to dr_annotation.h and dr_annotations.h. Done means agreeing on the include/app/ hierarchy and any header rename, updating all affected references, and confirming the project still builds.

Written by the indexing model from the issue text.