rollup merge of #20410: japaric/assoc-types

Conflicts:
	src/liballoc/lib.rs
	src/libcollections/lib.rs
	src/libcollections/slice.rs
	src/libcore/ops.rs
	src/libcore/prelude.rs
	src/libcore/ptr.rs
	src/librustc/middle/traits/project.rs
	src/libstd/c_str.rs
	src/libstd/io/mem.rs
	src/libstd/io/mod.rs
	src/libstd/lib.rs
	src/libstd/path/posix.rs
	src/libstd/path/windows.rs
	src/libstd/prelude.rs
	src/libstd/rt/exclusive.rs
	src/libsyntax/lib.rs
	src/test/compile-fail/issue-18566.rs
	src/test/run-pass/deref-mut-on-ref.rs
	src/test/run-pass/deref-on-ref.rs
	src/test/run-pass/dst-deref-mut.rs
	src/test/run-pass/dst-deref.rs
	src/test/run-pass/fixup-deref-mut.rs
	src/test/run-pass/issue-13264.rs
	src/test/run-pass/overloaded-autoderef-indexing.rs

src/liballoc/lib.rs

@@ -66,6 +66,7 @@
 #![no_std]
 #![allow(unknown_features)]
 #![feature(lang_items, phase, unsafe_destructor, default_type_params, old_orphan_check)]
+#![feature(associated_types)]
 
 #[phase(plugin, link)]
 extern crate core;