FullscreenUI: Re-enable most previously-missing settings

src/frontend-common/imgui_manager.h

@@ -56,6 +56,12 @@ ImFont* GetMediumFont();
 /// This font is allocated on demand.
 ImFont* GetLargeFont();
 
+/// Returns true if imgui wants to intercept text input.
+bool WantsTextInput();
+
+/// Called on the UI or CPU thread in response to a key press. String is UTF-8.
+void AddTextInput(std::string str);
+
 /// Called on the UI or CPU thread in response to mouse movement.
 void UpdateMousePosition(float x, float y);