sdl2: Button for "Clean" action
Add support for "Clean" action to the sdl2-client in the form of a new button. For now no key will be associated with it, as we want to keep (p) reserved for the old "Clean Pollution" action.
Add support for "Clean" action to the sdl2-client in the form of a new button. For now no key will be associated with it, as we want to keep (p) reserved for the old "Clean Pollution" action.