systemd 221 Adds an Alternative, Very Efficient D-Bus Client Library

systemd 221 is here to add the sd-event.h and sd-bus.h APIs (Application Programming Interfaces) to the official interface of libsystemd.so and declare them stable. Users are being informed by Lennart Poettering that the sd-bus API should be considered an alternative to the D-Bus client library, supporting both kdbus and D-Bus as transport backend while being very efficient and easy to use.