Merge pull request #3763 from esenapaj/patch-4

Follow-up for #3720 and #3759

Marlin/example_configurations/Felix/Configuration_DUAL.h

 //
 // Host Keepalive
 //
-// By default Marlin will send a busy status message to the host
+// When enabled Marlin will send a busy status message to the host
 // every couple of seconds when it can't accept commands.
 //
-//#define DISABLE_HOST_KEEPALIVE // Enable this option if your host doesn't like keepalive messages.
-#if DISABLED(DISABLE_HOST_KEEPALIVE)
-  #define DEFAULT_KEEPALIVE_INTERVAL 2 // Number of seconds between "busy" messages. Set with M113.
-#endif
+#define HOST_KEEPALIVE_FEATURE        // Disable this if your host doesn't like keepalive messages
+#define DEFAULT_KEEPALIVE_INTERVAL 2  // Number of seconds between "busy" messages. Set with M113.
 
 //
 // M100 Free Memory Watcher
 #define ABS_PREHEAT_HPB_TEMP 100
 #define ABS_PREHEAT_FAN_SPEED 255   // Insert Value between 0 and 255
 
+//
+// Print job timer
+//
+// Enable this option to automatically start and stop the
+// print job timer when M104 and M109 commands are received.
+//
+// In all cases the timer can be started and stopped using
+// the following commands:
+//
+// - M75  - Start the print job timer
+// - M76  - Pause the print job timer
+// - M77  - Stop the print job timer
+#define PRINTJOB_TIMER_AUTOSTART
 
 //
 // Print Counter