user32: Post WM_INPUT_DEVICE_CHANGE when registering for notifications
This seems to be relied on by some versions of this Unreal Engine input plugin
Note: I'm not sure how to deal with HID_USAGE_GENERIC_KEYPAD, which (I think) would fall under RIM_TYPEKEYBOARD. Do we need to store extra info to differentiate these from HID_USAGE_GENERIC_KEYBOARD or is there something in the device info struct that can differentiate them?