Include maximum clock frequency error in our dispersion

Add maxclockerror directive to set the stability of the clock (10 ppm by
default) and include it in our dispersion.

local.c

@@ -34,6 +34,7 @@
 #include <assert.h>
 #include <stddef.h>
 
+#include "conf.h"
 #include "local.h"
 #include "localp.h"
 #include "memory.h"
@@ -91,6 +92,8 @@ static DispersionNotifyListEntry dispersion_notify_list;
 static int precision_log;
 static double precision_quantum;
 
+static double max_clock_error;
+
 /* ================================================== */
 
 /* Define the number of increments of the system clock that we want
@@ -157,6 +160,8 @@ LCL_Initialise(void)
   temp_comp_ppm = 0.0;
 
   calculate_sys_precision();
+
+  max_clock_error = CNF_GetMaxClockError() * 1e-6;
 }
 
 /* ================================================== */
@@ -187,6 +192,14 @@ LCL_GetSysPrecisionAsQuantum(void)
 
 /* ================================================== */
 
+double
+LCL_GetMaxClockError(void)
+{
+  return max_clock_error;
+}
+
+/* ================================================== */
+
 void
 LCL_AddParameterChangeHandler(LCL_ParameterChangeHandler handler, void *anything)
 {