pkg/syscall: Fix darwin_amd64 syscalls. Fixes #51.

fmt.Println now works just fine on darwin_amd64 too, yay!
pkg/syscall: Fix darwin_amd64 syscalls take 2. Fixes #51.

This change includes more links to reference material and now makes
use of the carry flag to detect errors.
Merge pull request #60 from quarnster/master

pkg/syscall: Fix darwin_amd64 syscalls. Fixes #51.