Require the "unstable" feature for the C API.

Author: SimonSapin

.travis.yml

@@ -7,7 +7,8 @@ script:
   - cargo build
   - cargo doc
   - cargo test
-  - "(cd capi/ctest; ./build-and-test.sh)"
+  - cargo test --features unstable
+  - "if [ $TRAVIS_RUST_VERSION = nightly ]; then (cd capi/ctest; ./build-and-test.sh); fi"
 after_success: curl https://raw.githubusercontent.com/kmcallister/travis-doc-upload/master/travis-doc-upload.sh | sh
 notifications:
   webhooks: http://build.servo.org:54856/travis

capi/Cargo.toml

@@ -16,6 +16,7 @@ libc = "0.1"
 
 [dependencies.tendril]
 path = "../"
+features = ["unstable"]  # Drop flags and C API don’t play friends
 
 [build-dependencies]
 gcc = "0"

src/util.rs

@@ -4,7 +4,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#[cfg(feature = "unstable")] use core::nonzero::NonZero;
 use std::{slice, intrinsics};
 use std::mem;
 
@@ -41,6 +40,8 @@ pub unsafe fn copy_lifetime<'a, S: ?Sized, T: ?Sized + 'a>
     mem::transmute(ptr)
 }
 
+#[cfg(feature = "unstable")] pub use core::nonzero::NonZero;
+
 #[cfg(not(feature = "unstable"))]
 #[derive(Copy, Clone)]
 pub struct NonZero<T>(T);