Add toggle for AltGr alpha characters key display when Caps is on

Signed-off-by: Ray-V <ray-v@inbox.lv>
(cherry picked from commit 907f3d61aa)

src/VButton.cpp

@@ -91,8 +91,19 @@ void VButton::shiftCapsAltGrPressed(bool shift, bool caps, bool altGrState)
 {
 	if (altGrState)
 	{
-		// Caps does not seem to make any difference when AltGr is pressed
+		// If Caps is on, displayed alpha characters should be toggled from the AltGr case
-		if (shift)
+		if (caps)
+		{
+			if (shift)
+			{
+				TQPushButton::setText(altGrShiftText.lower());
+			}
+			else
+			{
+				TQPushButton::setText(altGrText.upper());
+			}
+		}
+		else if (shift)
 		{
 			TQPushButton::setText(altGrShiftText);
 		}