Opt into new box_patterns feature gate in various crates.

Namely: `collections` (used in `dlist.rs`), `syntax`, `rustc`,
`rustc_typeck`, `rustc_trans`, and `rustdoc`.

src/libcollections/lib.rs

@@ -24,6 +24,7 @@
 
 #![feature(alloc)]
 #![feature(box_syntax)]
+#![feature(box_patterns)]
 #![feature(core)]
 #![feature(hash)]
 #![feature(staged_api)]

src/librustc/lib.rs

@@ -23,6 +23,7 @@
       html_favicon_url = "http://www.rust-lang.org/favicon.ico",
       html_root_url = "http://doc.rust-lang.org/nightly/")]
 
+#![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(collections)]
 #![feature(core)]

src/librustc_trans/lib.rs

@@ -24,6 +24,7 @@
       html_root_url = "http://doc.rust-lang.org/nightly/")]
 
 #![feature(alloc)]
+#![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(collections)]
 #![feature(core)]

src/librustc_typeck/lib.rs

@@ -74,6 +74,7 @@
 
 #![allow(non_camel_case_types)]
 
+#![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(collections)]
 #![feature(core)]

src/librustdoc/lib.rs

@@ -18,6 +18,7 @@
        html_root_url = "http://doc.rust-lang.org/nightly/",
        html_playground_url = "http://play.rust-lang.org/")]
 
+#![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(collections)]
 #![feature(core)]

src/libsyntax/lib.rs

@@ -23,6 +23,7 @@
        html_favicon_url = "http://www.rust-lang.org/favicon.ico",
        html_root_url = "http://doc.rust-lang.org/nightly/")]
 
+#![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(collections)]
 #![feature(core)]