Fix travis dox

[kerautret]

PR Description

Fix travis Doxygen compilation for non Documention mode. (it was failing from some time)

Checklist

• Doxygen documentation of the code completed (classes, methods, types, members...).
• Main tool doxygen documentation (following existing documentation of DGtalTools documentation.
• Check if it follows the tools structure described in CONTRIBUTING.md
• New entry in the ChangeLog.md added.
• Update the readme with potentially a screenshot of the tools if it applies.
• No warning raised in Debug cmake mode (otherwise, Travis C.I. will fail).

[kerautret]

@dcoeurjo do you think that it could be merged ? After the travis Doxygen fix I have also tried to fix the doc upload which is no more sync here: http://dgtal.org/doc/tools/nightly/ since last June. So I follow the DGtal copy doc steps, but not sure of me for the change of url and ssh related keys ;).

[dcoeurjo]

mm.. let's merge this one and see what's going on.

[kerautret]

mm.. let's merge this one and see what's going on.

thanks, else I fix a typo and afterwards the doc copy looks failing;

/home/travis/.travis/job_stages: line 57: .travis/publish_doc.sh: Permission denied
I look by trying to update the key
=> same result