Add "TasksMax=1024" in 'guix-daemon.service'.

Suggested by Joram Schrijver <i+guix-devel@joram.io>.

* etc/guix-daemon.service.in (TasksMax): New value.

etc/guix-daemon.service.in

@@ -11,5 +11,8 @@ RemainAfterExit=yes
 StandardOutput=syslog
 StandardError=syslog
 
+# See <https://lists.gnu.org/archive/html/guix-devel/2016-04/msg00608.html>.
+TasksMax=1024
+
 [Install]
 WantedBy=multi-user.target