1.9.0
Prepare for version 1.9.0

1. Update ceres-solver.spec with version bump
   and a new package description.
2. Update the docs to refer to 1.9.0
3. Update version history.
4. Change build requirements for Android to be r9d.

Change-Id: Ibab27976b214a11549cb2688b91f791a6388b0b5
5 files changed