/usr/include/postgresql/10/server/replication/ is in postgresql-server-dev-10 10.3-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/postgresql/10/server/replication/basebackup.h
/usr/include/postgresql/10/server/replication/decode.h
/usr/include/postgresql/10/server/replication/logical.h
/usr/include/postgresql/10/server/replication/logicalfuncs.h
/usr/include/postgresql/10/server/replication/logicallauncher.h
/usr/include/postgresql/10/server/replication/logicalproto.h
/usr/include/postgresql/10/server/replication/logicalrelation.h
/usr/include/postgresql/10/server/replication/logicalworker.h
/usr/include/postgresql/10/server/replication/message.h
/usr/include/postgresql/10/server/replication/origin.h
/usr/include/postgresql/10/server/replication/output_plugin.h
/usr/include/postgresql/10/server/replication/pgoutput.h
/usr/include/postgresql/10/server/replication/reorderbuffer.h
/usr/include/postgresql/10/server/replication/slot.h
/usr/include/postgresql/10/server/replication/snapbuild.h
/usr/include/postgresql/10/server/replication/syncrep.h
/usr/include/postgresql/10/server/replication/walreceiver.h
/usr/include/postgresql/10/server/replication/walsender.h
/usr/include/postgresql/10/server/replication/walsender_private.h
/usr/include/postgresql/10/server/replication/worker_internal.h