jh-ffi error
Strangely i installed with rust-up the nighly but i see stable channel..any ideas why not compile?

# cargo build --release
   Compiling skein-ffi v0.0.1
   Compiling jh-ffi v0.0.2
   Compiling serde_derive v1.0.27
   Compiling env_logger v0.4.3
error[E0554]: #![feature] may not be used on the stable release channel
 --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/skein-ffi-0.0.1/src/lib.rs:2:1
  |
2 | #![feature(libc)]
  | ^^^^^^^^^^^^^^^^^

error: aborting due to previous error

error[E0554]: #![feature] may not be used on the stable release channel
 --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/jh-ffi-0.0.2/src/lib.rs:2:1
  |
2 | #![feature(libc)]
  | ^^^^^^^^^^^^^^^^^

error: aborting due to previous error

error: Could not compile `jh-ffi`.
warning: build failed, waiting for other jobs to finish...
The following warnings were emitted during compilation:

warning: ext/skein/c_skein.c: In function ‘Skein_256_Final’:
warning: ext/skein/c_skein.c:1360:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
warning: ext/skein/c_skein.c: In function ‘Skein_512_Final’:
warning: ext/skein/c_skein.c:1560:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
warning: ext/skein/c_skein.c: In function ‘Skein1024_Final’:
warning: ext/skein/c_skein.c:1758:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]

error: Could not compile `skein-ffi`.
warning: build failed, waiting for other jobs to finish...
