* gnu/services/base.scm (<syslog-configuration>): New variable. (syslog-service-type): Use <syslog-configuration>. (syslog-service): Use <syslog-configuration>. * gnu/tests/base.scm (%avahi-os): Use <syslog-configuration>. * doc/guix.texi (syslog-configuration-type): Add @deftp. (syslog-service): Update @deffn.