Fix T43159: Copying of linked datablocks using relpath leads to invalid paths in new copies.

Propper fix reverting most of rB60e70c0c6014e5, which was only partial specific fix.
This code uses generic `BKE_id_lib_local_paths()` func to handle all possible paths.

Reviewers: sergey, campbellbarton

Differential Revision: https://developer.blender.org/D977

source/blender/blenkernel/intern/speaker.c

@@ -67,6 +67,10 @@ Speaker *BKE_speaker_copy(Speaker *spk)
 	if (spkn->sound)
 		spkn->sound->id.us++;
 
+	if (spk->id.lib) {
+		BKE_id_lib_local_paths(G.main, spk->id.lib, &spkn->id);
+	}
+
 	return spkn;
 }