Offset-based mmap

See merge request redox-os/redoxfs!61

Prefer libc over redox_syscall in mount.

See merge request !60

Fix unnecessary mutable variable warning

See merge request redox-os/redoxfs!59

Fix image unmounting & tooling to work under gentoo and MacOS

See merge request redox-os/redoxfs!58

This fixes unmounting with gentoo. This function will be use by the installer to
unmount the image after the build.

Migrate from fuse to fuser

See merge request redox-os/redoxfs!57

Fix bug where root could not remove other users' files

Closes redox#1366

See merge request redox-os/redoxfs!56

These will only exist in the middle of rename