Move M110 to cpp

Marlin/src/Marlin.cpp

@@ -374,8 +374,6 @@ bool pin_is_protected(const int8_t pin) {
   return false;
 }
 
-#include "gcode/host/M110.h"
-
 #include "gcode/control/M111.h"
 
 #if ENABLED(HOST_KEEPALIVE_FEATURE)

Marlin/src/gcode/gcode.cpp

@@ -124,7 +124,6 @@ extern void gcode_M83();
 extern void gcode_M85();
 extern void gcode_M92();
 extern void gcode_M100();
-extern void gcode_M110();
 extern void gcode_M111();
 extern void gcode_M113();
 extern void gcode_M114();
@@ -448,9 +447,7 @@ void GcodeSuite::process_next_command() {
       case 104: M104(); break;    // M104: Set hot end temperature
       case 109: M109(); break;    // M109: Wait for hotend temperature to reach target
 
-      case 110: // M110: Set Current Line Number
-        gcode_M110();
-        break;
+      case 110: M110(); break;    // M110: Set Current Line Number
 
       case 111: // M111: Set debug level
         gcode_M111();

Marlin/src/gcode/host/M110.h → Marlin/src/gcode/host/M110.cpp

@@ -20,11 +20,12 @@
  *
  */
 
-#include "../queue.h"
+#include "../gcode.h"
+#include "../queue.h" // for gcode_LastN
 
 /**
  * M110: Set Current Line Number
  */
-void gcode_M110() {
+void GcodeSuite::M110() {
   if (parser.seenval('N')) gcode_LastN = parser.value_long();
 }