You may find an up-to-date version of these source files online:
http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h
- http://cgit.freedesktop.org/systemd/systemd/plain/src/sd-daemon.c
+ http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c
This should compile on non-Linux systems, too, but with the
exception of the sd_is_xxx() calls all functions will become NOPs.