Use real libcore instead of renamed libstd

Author: dhardy

src/distributions/uniform.rs

@@ -939,7 +939,7 @@ mod tests {
               not(target_arch = "wasm32"),
               not(target_arch = "asmjs")))]
     fn test_float_assertions() {
-        use core::panic::catch_unwind;
+        use std::panic::catch_unwind;
         use super::SampleUniform;
         fn range<T: SampleUniform>(low: T, high: T) {
             let mut rng = ::test::rng(253);

src/lib.rs

@@ -233,7 +233,7 @@
 #![cfg_attr(feature = "wasm-bindgen", feature(use_extern_macros))]
 #![cfg_attr(feature = "wasm-bindgen", feature(wasm_import_module))]
 
-#[cfg(feature="std")] extern crate std as core;
+#[cfg(feature = "std")] extern crate core;
 #[cfg(all(feature = "alloc", not(feature="std")))] extern crate alloc;
 
 #[cfg(all(target_arch="wasm32", not(target_os="emscripten"), feature="stdweb"))]