Use correct numeric types for events

[eagleflo]

After the recent int / uint debacle and rename to isize and usize, I was wondering why their use is so prevalent in rust-sdl2. As far as I can tell they should not be used as a general purpose integer type in Rust.

This pull request changes the integer types used in events to match the definitions found in SDL_event.h. There is much less casting involved after this change. This will likely break a lot of code, but the recent int -> isize transition also breaks the same code, so I felt this would be a good opportunity for this change.

I also noticed that touch and gesture events use f64 where SDL2 uses f32. This implies greater accuracy than SDL2 provides, so I changed those back to f32, but I'm not sure if this is the right way to go -- those commits can be easily dropped if needed.

I assume you will want to pull jpernst's recent 1.0 alpha fixes, so I based this branch on top of those commits.

[ketsuban]

I suspect you'll want to deal with the warnings about the deprecated i/u suffixes on integer literals before this can be merged, since that's part of removing unnecessary uses of int/uint.

[jpernst]

Woops, good catch on the suffixes. I missed those on my initial pass since I forgot to rebuild sdl2-sys and missed the warnings. I've fixed them in my PR, so this should probably be rebased.

Thanks for doing this though. I was meaning to do it but kept putting it off since it's such a slog to go through every use in every API one by one.

[eagleflo]

Rebased.

[AngryLawyer]

Grand, this is brilliant.