Merge upstream changes from Marlin 2.1.1

Marlin/src/lcd/extui/dgus_reloaded/DGUSDisplay.h

@@ -16,7 +16,7 @@
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  *
  */
 #pragma once
@@ -69,6 +69,9 @@ public:
   // Until now I did not need to actively read from the display. That's why there is no ReadVariable
   // (I extensively use the auto upload of the display)
 
+  // Read GUI and OS version from screen
+  static void ReadVersions();
+
   // Force display into another screen.
   static void SwitchScreen(DGUS_Screen screen);
   // Play sounds using the display speaker.
@@ -96,9 +99,9 @@ public:
   static size_t GetFreeTxBuffer();
   static void FlushTx();
 
-  // Checks two things: Can we confirm the presence of the display and has we initiliazed it.
+  // Checks two things: Can we confirm the presence of the display and has we initialized it.
   // (both boils down that the display answered to our chatting)
-  static inline bool IsInitialized() {
+  static bool IsInitialized() {
     return initialized;
   }