InputConfigDialog: Don't show "..." for complicated expressions

Just show the actual expression. We need to do a bit of mangling
here as wx has no way to turn off mnemonics parsing, so do that
as well.

Source/Core/InputCommon/Src/ControllerInterface/ExpressionParser.h

@@ -51,7 +51,6 @@ public:
 	ControlState GetValue();
 	void SetValue (ControlState state);
 	int num_controls;
-	bool is_complicated;
 	ExpressionNode *node;
 };