* Joystick hotplug support (#4141)
* use SDL_PollEvent instead of SDL_JoystickUpdate
Register hot plugged controller by GUID if they were configured in a previous session
* Move SDL_PollEvent into its own thread
* Don't store SDLJoystick pointer in Input Device; Get pointer on each GetStatus call
* Fix that joystick_list gets cleared after SDL_Quit
* Add VirtualJoystick for InputDevices thats never nullptr
* fixup! Add VirtualJoystick for InputDevices thats never nullptr
* fixup! fixup! Add VirtualJoystick for InputDevices thats never nullptr
* Remove SDL_GameController, make SDL_Joystick* unique_ptr
* fixup! Remove SDL_GameController, make SDL_Joystick* unique_ptr
* Adressed feedback; fixed handling of same guid reconnects
* fixup! Adressed feedback; fixed handling of same guid reconnects
* merge the two joystick_lists into one
* make SDLJoystick a member of VirtualJoystick
* fixup! make SDLJoystick a member of VirtualJoystick
* fixup! make SDLJoystick a member of VirtualJoystick
* fixup! fixup! make SDLJoystick a member of VirtualJoystick
* SDLJoystick: Addressed review comments
* Address one missed review comment
Modules didn't correctly define their dependencies before, which relied
on the frontends implicitly including every module for linking to
succeed.
Also changed every target_link_libraries call to specify visibility of
dependencies to avoid leaking definitions to dependents when not
necessary.
Tobias