Use gettext plural features

Make use of the plural features of gettext to handle plural forms
correctly instead of using the plural form even if the singular form
should be used.

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/dmon.c

@@ -194,8 +194,9 @@ dmon_start (int parent_exit_status)
             DMON_LOG (_("error while sending notification\n"));
         }
 
-      DMON_LOG (_("sleeping at %s for %d seconds\n"), nowstr (),
-                DMON_SLEEP_TIME);
+      DMON_LOG (ngettext ("sleeping at %s for %d second\n",
+                          "sleeping at %s for %d seconds\n",
+                          DMON_SLEEP_TIME), nowstr (), DMON_SLEEP_TIME);
       psleep (DMON_SLEEP_TIME);
       DMON_LOG (_("awakened at %s\n"), nowstr ());
     }