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/libstd/io/mod.rs

@@ -227,6 +227,7 @@ use libc;
 use ops::{BitOr, BitAnd, Sub};
 use os;
 use option::{Option, Some, None};
+use owned::Box;
 use path::Path;
 use result::{Ok, Err, Result};
 use str::StrSlice;
@@ -811,7 +812,7 @@ pub trait Reader {
     }
 }
 
-impl Reader for ~Reader {
+impl Reader for Box<Reader> {
     fn read(&mut self, buf: &mut [u8]) -> IoResult<uint> { self.read(buf) }
 }
 
@@ -1052,7 +1053,7 @@ pub trait Writer {
     }
 }
 
-impl Writer for ~Writer {
+impl Writer for Box<Writer> {
     fn write(&mut self, buf: &[u8]) -> IoResult<()> { self.write(buf) }
     fn flush(&mut self) -> IoResult<()> { self.flush() }
 }