feat(linux): Add symbols file

Debian/lintian recommends to add a symbols file which allows to
check for API changes. The package build on Jenkins now has an
additional build step that will compare the API of the newly
built package with the committed symbols file and will fail the
build if the API changed and we didn't update the symbols file
yet. The current symbols file gets stored as build artifact, so
it can easily be copied from Jenkins.

During the build of the binary package this check is also run but
won't fail the build.