Merge branch 'master' into 'master'

Update url away from github

See merge request redox-os/syscall!31

README.md

 # syscall
-[Redox OS](https://github.com/redox-os/redox)'s syscall API
+[Redox OS](https://gitlab.redox-os.org/redox-os/redox)'s syscall API
 
 [![MIT licensed](https://img.shields.io/badge/license-MIT-blue.svg)](./LICENSE)
 [![crates.io](http://meritbadge.herokuapp.com/redox_syscall)](https://crates.io/crates/redox_syscall)