Better LCD message when heating needed

Marlin/src/feature/pause.cpp

     SERIAL_ERRORLNPGM(MSG_HOTEND_TOO_COLD);
 
     #if ENABLED(ULTIPANEL)
-      if (show_lcd) // Show status screen
+      if (show_lcd) { // Show status screen
         lcd_advanced_pause_show_message(ADVANCED_PAUSE_MESSAGE_STATUS);
+        LCD_MESSAGEPGM(MSG_M600_TOO_COLD);
+      }
     #endif
 
     return false; // unable to reach safe temperature

Marlin/src/lcd/language/language_en.h

 #ifndef MSG_ERR_PROBING_FAILED
   #define MSG_ERR_PROBING_FAILED              _UxGT("Probing failed")
 #endif
+#ifndef MSG_M600_TOO_COLD
+  #define MSG_M600_TOO_COLD                   _UxGT("M600: Too cold")
+#endif
 
 //
 // Filament Change screens show up to 3 lines on a 4-line display