gencpp: 0.5.3-0 in 'indigo/distribution.yaml' [bloom]

Increasing version of package(s) in repository `gencpp` to `0.5.3-0`:

- upstream repository: git@github.com:ros/gencpp.git
- release repository: https://github.com/ros-gbp/gencpp-release.git
- distro file: `indigo/distribution.yaml`
- bloom version: `0.5.16`
- previous version for package: `0.5.2-0`

## gencpp

```
* remove copyright header from generated code (#20 <https://github.com/ros/gencpp/issues/20>)
```