In lirc-core-0.9.4c, lircd-setup.service is missing (it's already missing in
the original lirc-0.9.4c tarball), but it is wanted by lircd.service.

/usr/lib/systemd/system/lircd-setup.service invokes /usr/sbin/lircd-setup,
which executes the [modinit] section of /etc/lirc/lirc_options.conf. In my
case, it should have modprobed the serial_ir driver; since that was skipped,
the driver was not loaded, and lirc wouldn't work.

lircd-setup is included in the lirc-core-0.9.4c package, so I simply installed
lircd-setup.service from the lirc-0.9.4d tarball (this file is still the same
in lirc-0.10.1). lirc now works fine for me.