General: Mark a handful of deduced const variables as const explicitly

Same behavior, but makes it explicit to the reader that these are const.

Prevents cases where the reader might assume that just because the
variable isn't const qualified that it must be mutable, when it actually
isn't.

Runtime/GuiSys/CGuiFrame.cpp

@@ -187,11 +187,14 @@ void CGuiFrame::LoadWidgetsInGame(CInputStream& in, CSimplePool* sp) {
 }
 
 void CGuiFrame::ProcessUserInput(const CFinalInput& input) const {
-  if (input.ControllerIdx() != 0)
+  if (input.ControllerIdx() != 0) {
     return;
-  for (auto& widget : x2c_widgets) {
-    if (widget->GetIsActive())
+  }
+
+  for (const auto& widget : x2c_widgets) {
+    if (widget->GetIsActive()) {
       widget->ProcessUserInput(input);
+    }
   }
 }