refclock: check all driver options

In each driver provide a list of supported options and abort when an
unknown option is specified in the refclock directive.

refclock_shm.c

@@ -59,10 +59,13 @@ struct shmTime {
 };
 
 static int shm_initialise(RCL_Instance instance) {
+  const char *options[] = {"perm", NULL};
   int id, param, perm;
   char *s;
   struct shmTime *shm;
 
+  RCL_CheckDriverOptions(instance, options);
+
   param = atoi(RCL_GetDriverParameter(instance));
   s = RCL_GetDriverOption(instance, "perm");
   perm = s ? strtol(s, NULL, 8) & 0777 : 0600;