Reduce CPU usage of serial event generator.

There's no reason for the select(2) call to have a 1ms timeout. At that
point, it's basically a busy loop. A 100ms timeout greatly reduces CPU
usage while retaining fairly quick responsiveness to port closure.

Closes #36.

src/main/c/src/SerialImp.c

@@ -4146,7 +4146,7 @@ int initialise_event_info_struct( struct event_info_struct *eis )
 	if (eis->fd < FD_SETSIZE && eis->fd > 0) {
 		FD_SET( eis->fd, &eis->rfds );
 		eis->tv_sleep.tv_sec = 0;
-		eis->tv_sleep.tv_usec = 1000;
+		eis->tv_sleep.tv_usec = 100 * 1000;
 		eis->initialised = 1;
 		return( 1 );
 	} else {