Optionally Enriched the info displayed at the beginning of debug message lines as discussed in Issue #66

sim> set debug -r -a -t -p somefile

    -a   produces seconds.msec time format
    -t    produces hh:mm:ss.msec time format
    -r    causes time values displayed to be relative to the wall clock time when the 'set debug' command was issued
    -r   by itself will cause default of -t

    -a and -t can both be specified if desired

    -p   adds display of current PC value to the debug timestamp output

sim> show debug

sim_timer.h

@@ -124,3 +124,4 @@ extern t_bool sim_asynch_timer;
 extern DEVICE sim_timer_dev;
 
 #endif
+