Add/correct description for some sysctl variables where it was missing.

The description field is unused in -stable, so the MFC there is equivalent
to a comment. It can be done at any time, i am just setting a reminder
in 45 days when hopefully we are past 4.5-release.

MFC after: 45 days

sys/kern/init_main.c

@@ -458,7 +458,8 @@ static char init_path[MAXPATHLEN] =
 #else
     "/sbin/init:/sbin/oinit:/sbin/init.bak:/stand/sysinstall";
 #endif
-SYSCTL_STRING(_kern, OID_AUTO, init_path, CTLFLAG_RD, init_path, 0, "");
+SYSCTL_STRING(_kern, OID_AUTO, init_path, CTLFLAG_RD, init_path, 0,
+	"Path used to search the init process");
 
 /*
  * Start the initial user process; try exec'ing each pathname in init_path.

sys/kern/kern_clock.c

@@ -493,4 +493,5 @@ sysctl_kern_clockrate(SYSCTL_HANDLER_ARGS)
 }
 
 SYSCTL_PROC(_kern, KERN_CLOCKRATE, clockrate, CTLTYPE_STRUCT|CTLFLAG_RD,
-	0, 0, sysctl_kern_clockrate, "S,clockinfo","");
+	0, 0, sysctl_kern_clockrate, "S,clockinfo",
+	"Rate and period of various kernel clocks");

sys/kern/kern_mib.c

@@ -83,7 +83,7 @@ SYSCTL_NODE(, OID_AUTO, regression, CTLFLAG_RW, 0,
 #endif
 
 SYSCTL_STRING(_kern, KERN_OSRELEASE, osrelease, CTLFLAG_RD,
-    osrelease, 0, "Operating system type");
+    osrelease, 0, "Operating system release");
 
 SYSCTL_INT(_kern, KERN_OSREV, osrevision, CTLFLAG_RD,
     0, BSD, "Operating system revision");

sys/kern/kern_synch.c

@@ -112,7 +112,8 @@ sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
 }
 
 SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW,
-	0, sizeof sched_quantum, sysctl_kern_quantum, "I", "");
+	0, sizeof sched_quantum, sysctl_kern_quantum, "I",
+	"Roundrobin scheduling quantum in microseconds");
 
 /*
  * Arrange to reschedule if necessary, taking the priorities and