* gnu/services/base.scm (<guix-configuration>)[log-file]: New field.
(guix-shepherd-service): Pass #:log-file to 'make-forkexec-constructor'.
* gnu/services/admin.scm (simple-rotation-config): Take a list of
files and join them with commas.
(%default-rotations): Add /var/log/guix-daemon.log.
* doc/guix.texi (Base Services): Document it.
* gnu/services/admin.scm (%rotated-files): Add "/var/log/maillog".
(syslog-rotation-config): Change parameter to 'files'. Return a
string-append gexp for all of FILES.
(simple-rotation-config): Remove unnecessary 'postrotate' and
'endscript'.
(%default-rotations): Adjust accordingly.
