xpc-sys -> 0.5.1

Merge pull request #22 from mach-kernel/120423/xpc-object-default

xpc-sys: Don't xpc_release NULLs

Merge pull request #18 from mach-kernel/090622/update-deps-fix-arm

Update to latest crates, add aarch to build targets, misc cleanups

Merge pull request #18 from mach-kernel/090622/update-deps-fix-arm

Update to latest crates, add aarch to build targets, misc cleanups

Merge pull request #16 from mach-kernel/093021/move-querybuilder

Move QueryBuilder trait to xpc-sys crate

Merge pull request #14 from mach-kernel/fix-env-macro

Fix env macro usage

Merge pull request #13 from mach-kernel/another-xpc-retain-fix

Better XPC release/retain usage, plist handling, omnibox usability

Merge pull request #13 from mach-kernel/another-xpc-retain-fix

Better XPC release/retain usage, plist handling, omnibox usability

Merge pull request #12 from mach-kernel/iostat/rust-feedback

Rust feedback / improvements