librustc: Remove ~EXPR, ~TYPE, and ~PAT from the language, except

for `~str`/`~[]`.

Note that `~self` still remains, since I forgot to add support for
`Box<self>` before the snapshot.

How to update your code:

* Instead of `~EXPR`, you should write `box EXPR`.

* Instead of `~TYPE`, you should write `Box<Type>`.

* Instead of `~PATTERN`, you should write `box PATTERN`.

[breaking-change]

src/test/compile-fail/struct-fields-missing.rs

@@ -8,9 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+
 struct BuildData {
     foo: int,
-    bar: ~int
+    bar: Box<int>,
 }
 
 fn main() {