This ensures proper dependencies when a package has a Build-Depends on a
higher version of libudev-dev or libsystemd-dev then what it gets from
the used symbols.
See Debian policy 8.6.3.2 and deb-symbols(5).
- Add two new symbols for libudev1.
- Remove private symbol from libgudev-1.0-0. This symbol was never part of
the public API and not used anywhere so we don't need a soname bump.