Add macOS SCSI support via IOKit SCSITaskDeviceInterface

IOKit backend for macOS optical drives. Accepts BSD device paths
(/dev/disk2), walks IORegistry to find authoring device, sends
SCSI commands through SCSITaskDeviceInterface COM vtable.

build.rs

@@ -0,0 +1,7 @@
+fn main() {
+    #[cfg(target_os = "macos")]
+    {
+        println!("cargo:rustc-link-lib=framework=IOKit");
+        println!("cargo:rustc-link-lib=framework=CoreFoundation");
+    }
+}