The ELF magic cannot work for consumers of our shard library, since they
are in a different module. Hence make all the ELF magic private, and
instead introduce a public function to register additional static
mapping table.
__attribute__((used)) is not enough to force static variables to
be carried over to a compiled program from a library. Mappings defined
in libsystemd-shared.a were not visible in the compiled binaries.
To ensure that the mappings are present in the final binary, the
tables are made non-static and are given a real unique name by which
they can be referenced.
To use a mapping defined not in the local compilation unit (e.g. in
a library) a reference to the mapping table is added. This is done
by including a declaration in the header file.
Expected values in test-engine are fixed to reflect the new mappings.
