std: Rename Show/String to Debug/Display

This commit is an implementation of [RFC 565][rfc] which is a stabilization of
the `std::fmt` module and the implementations of various formatting traits.
Specifically, the following changes were performed:

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0565-show-string-guidelines.md

* The `Show` trait is now deprecated, it was renamed to `Debug`
* The `String` trait is now deprecated, it was renamed to `Display`
* Many `Debug` and `Display` implementations were audited in accordance with the
  RFC and audited implementations now have the `#[stable]` attribute
  * Integers and floats no longer print a suffix
  * Smart pointers no longer print details that they are a smart pointer
  * Paths with `Debug` are now quoted and escape characters
* The `unwrap` methods on `Result` now require `Display` instead of `Debug`
* The `Error` trait no longer has a `detail` method and now requires that
  `Display` must be implemented. With the loss of `String`, this has moved into
  libcore.
* `impl<E: Error> FromError<E> for Box<Error>` now exists
* `derive(Show)` has been renamed to `derive(Debug)`. This is not currently
  warned about due to warnings being emitted on stage1+

While backwards compatibility is attempted to be maintained with a blanket
implementation of `Display` for the old `String` trait (and the same for
`Show`/`Debug`) this is still a breaking change due to primitives no longer
implementing `String` as well as modifications such as `unwrap` and the `Error`
trait. Most code is fairly straightforward to update with a rename or tweaks of
method calls.

[breaking-change]
Closes #21436

src/libstd/io/mod.rs

@@ -228,13 +228,12 @@ pub use self::FileAccess::*;
 pub use self::IoErrorKind::*;
 
 use char::CharExt;
-use clone::Clone;
 use default::Default;
-use error::{FromError, Error};
+use error::Error;
 use fmt;
 use int;
 use iter::{Iterator, IteratorExt};
-use marker::{Sized, Send};
+use marker::Sized;
 use mem::transmute;
 use ops::FnOnce;
 use option::Option;
@@ -340,7 +339,8 @@ impl IoError {
     }
 }
 
-impl fmt::String for IoError {
+#[stable]
+impl fmt::Display for IoError {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         match *self {
             IoError { kind: OtherIoError, desc: "unknown error", detail: Some(ref detail) } =>
@@ -354,19 +354,7 @@ impl fmt::String for IoError {
 }
 
 impl Error for IoError {
-    fn description(&self) -> &str {
-        self.desc
-    }
-
-    fn detail(&self) -> Option<String> {
-        self.detail.clone()
-    }
-}
-
-impl FromError<IoError> for Box<Error + Send> {
-    fn from_error(err: IoError) -> Box<Error + Send> {
-        box err
-    }
+    fn description(&self) -> &str { self.desc }
 }
 
 /// A list specifying general categories of I/O error.
@@ -1781,6 +1769,7 @@ pub struct UnstableFileStat {
 bitflags! {
     /// A set of permissions for a file or directory is represented by a set of
     /// flags which are or'd together.
+    #[derive(Show)]
     flags FilePermission: u32 {
         const USER_READ     = 0o400,
         const USER_WRITE    = 0o200,
@@ -1822,13 +1811,8 @@ impl Default for FilePermission {
     fn default() -> FilePermission { FilePermission::empty() }
 }
 
-impl fmt::Show for FilePermission {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(self, f)
-    }
-}
-
-impl fmt::String for FilePermission {
+#[stable]
+impl fmt::Display for FilePermission {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{:04o}", self.bits)
     }