xinput usage should load the local xinput DLL dynamically

Hello all.

It's a real shame that you statically link xinput. This makes it so that if a person doesn't have xinput installed, or if they have a different xinput version than what the program was compiled with, the program won't run. The fix for this is very simple, you simply load the xinput library dynamically at runtime as part of the setup when xinput is told to start and it spawns the background thread. I've got a fully working example here: https://github.com/Lokathor/rusty-xinput

Feel free to incorporate that entire crate into this crate or just as much as you like. It's only 632 lines total including all comments and all that, so it should be very easy to read and understand. The real workhorse here is dynamic_load_xinput