gilrs-core-azul 0.6.9

Minimal event-based abstraction for working with gamepads (azul fork of gilrs-core: redirects libudev-sys -> libudev-sys-azul so it cross-compiles to Linux hosts without libudev; plus `Gamepad::serial()` (IOKit kIOHIDSerialNumberKey on macOS); otherwise identical to upstream 0.6.8)