Merge remote-tracking branch 'nrc/sized-2' into rollup

Conflicts:
	src/liballoc/boxed.rs
	src/libcollections/btree/map.rs
	src/libcollections/slice.rs
	src/libcore/borrow.rs
	src/libcore/cmp.rs
	src/libcore/ops.rs
	src/libstd/c_str.rs
	src/libstd/collections/hash/map.rs
	src/libsyntax/parse/obsolete.rs
	src/test/compile-fail/unboxed-closure-sugar-default.rs
	src/test/compile-fail/unboxed-closure-sugar-equiv.rs
	src/test/compile-fail/unboxed-closure-sugar-lifetime-elision.rs
	src/test/compile-fail/unboxed-closure-sugar-region.rs
	src/test/compile-fail/unsized3.rs
	src/test/run-pass/associated-types-conditional-dispatch.rs

src/libcore/str/mod.rs

@@ -1155,7 +1155,7 @@ impl Str for str {
     fn as_slice<'a>(&'a self) -> &'a str { self }
 }
 
-impl<'a, Sized? S> Str for &'a S where S: Str {
+impl<'a, S: ?Sized> Str for &'a S where S: Str {
     #[inline]
     fn as_slice(&self) -> &str { Str::as_slice(*self) }
 }