The previous code could potentially be a compilation issue waiting to
occur, given we forward declare the type for a std::unique_ptr. If the
complete definition of the forward declared type isn't visible in a
translation unit that the class is used in, then it would fail to
compile.
Defaulting the destructor in a cpp file ensures the std::unique_ptr's
destructor is only invoked where its complete type is known.
* Added a context menu on the buttons including Clear & Restore Default
* Allow clearing (unsetting) inputs. Added a Clear All button
* Allow restoring a single input to default (instead of all)
* Add infrastructure to poll joystick input and get ParamPackages
* Generalize the callbacks in configure_input.cpp and add buttons for analog sticks
* Use the polling classes in the input dialog
* Fix includes
* Formatting fix
* Include real header instead of forward declaring, to fix compiler error
* Split up pair and add deadzone for joystick configuration
* Pass ParamPackages by reference to callback
* fix formatting
* getPollers -> GetPollers
* Add forward declarations and simplify code a bit
* Update joysticks before opening them
* Fix mixup between joystick IDs and device indices
