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_phc.c

@@ -56,10 +56,13 @@ static void read_ext_pulse(int sockfd, int event, void *anything);
 
 static int phc_initialise(RCL_Instance instance)
 {
+  const char *options[] = {"nocrossts", "extpps", "pin", "channel", "clear", NULL};
   struct phc_instance *phc;
   int phc_fd, rising_edge;
   char *path, *s;
 
+  RCL_CheckDriverOptions(instance, options);
+
   path = RCL_GetDriverParameter(instance);
  
   phc_fd = SYS_Linux_OpenPHC(path, 0);