Windows: Implement DeviceEvents

[francesca64]

Fixes #467

All variants other than Text have been implemented. While Text can be implemented using ToUnicode, that doesn't play nice with dead keys, IME, etc.

Most of the mouse DeviceEvents were already implemented, but due to the flags that were used when registering for raw input events, they only worked when the window was in the foreground.

This is also a step forward for #338, as DeviceIds are no longer useless on Windows. On DeviceEvents, the DeviceId contains that device's handle. While that handle could ostensibly be used by developers to query device information, my actual reason for choosing it is because it's simply a very easy way to handle this. As a fun bonus, this enabled me to create this method:

DevideIdExt::get_persistent_identifier() -> Option<String>

Using this gives you a unique identifier for the device that persists across replugs/reboots/etc., so it's ideal for something like device-specific configuration.

There's a notable caveat to the new DeviceIds, which is that the value will always be 0 for a WindowEvent. There doesn't seem to be any straightforward way around this limitation.

I was concerned that multi-window applications would receive n copies of every DeviceEvent, but Windows only sends them to one window per application.

Lastly, there's a chance that these additions will cause antivirus/etc. software to detect winit applications as keyloggers. I don't know how likely that is to actually happen to people, but if it does become an issue, the raw input code is neatly sequestered and would be easy to make optional during compilation.

[francesca64]

(I need to make sure I remember to re-export DeviceIdExt from glutin)

[Ralith]

get_persistent_identifier

This can be implemented on Linux using udev_device_get_sysattr_value with "idVendor", "idProduct", and "serial", on the device node obtained by XIGetProperty on the "Device Node" atom. Would be pretty sweet to have as a portable API.

[francesca64]

@Ralith thanks for the info. That sounds like a fun thing to implement, so I'll add it to my to-do list.