Generated source tarball is missing some files

As eolivelli pointed out:

I see differences between the contents of the source tarball and the
git tag (using Meld, as suggested by Patrick some month ago), namely:

• there is not checkstyleSuppressions.xml file, and mvn
  checkstyle:check fails (it is not bound to the default lifecycle, so
  mvn clean install still works)
• there are ".c" generated files, they should not be part of the source release
• there is not "dev" directory
• there is not .travis.yml file

Note: only affects branch-3.5.