Revert stabilizing integer::BITS.

compiler/rustc_data_structures/src/lib.rs

@@ -13,6 +13,7 @@
 #![feature(unboxed_closures)]
 #![feature(generator_trait)]
 #![feature(fn_traits)]
+#![feature(int_bits_const)]
 #![feature(min_specialization)]
 #![feature(auto_traits)]
 #![feature(nll)]

compiler/rustc_serialize/src/lib.rs

@@ -17,6 +17,7 @@ Core encoding and decoding interfaces.
 #![feature(min_specialization)]
 #![feature(vec_spare_capacity)]
 #![feature(core_intrinsics)]
+#![feature(int_bits_const)]
 #![feature(maybe_uninit_slice)]
 #![feature(new_uninit)]
 #![cfg_attr(test, feature(test))]

compiler/rustc_serialize/tests/leb128.rs

@@ -1,3 +1,4 @@
+#![feature(int_bits_const)]
 #![feature(maybe_uninit_slice)]
 #![feature(maybe_uninit_uninit_array)]