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
diff --git a/src/libcollections/ring_buf.rs b/src/libcollections/ring_buf.rs
index b9cb4be..badd7a8 100644
--- a/src/libcollections/ring_buf.rs
+++ b/src/libcollections/ring_buf.rs
@@ -1611,7 +1611,7 @@
 }
 
 #[stable]
-impl<T: fmt::Show> fmt::Show for RingBuf<T> {
+impl<T: fmt::Debug> fmt::Debug for RingBuf<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         try!(write!(f, "RingBuf ["));
 
@@ -1630,7 +1630,7 @@
     use self::Taggypar::*;
     use prelude::*;
     use core::iter;
-    use std::fmt::Show;
+    use std::fmt::Debug;
     use std::hash::{self, SipHasher};
     use test::Bencher;
     use test;
@@ -1678,7 +1678,7 @@
     }
 
     #[cfg(test)]
-    fn test_parameterized<T:Clone + PartialEq + Show>(a: T, b: T, c: T, d: T) {
+    fn test_parameterized<T:Clone + PartialEq + Debug>(a: T, b: T, c: T, d: T) {
         let mut deq = RingBuf::new();
         assert_eq!(deq.len(), 0);
         deq.push_front(a.clone());
@@ -2302,7 +2302,7 @@
     #[test]
     fn test_show() {
         let ringbuf: RingBuf<int> = range(0i, 10).collect();
-        assert_eq!(format!("{:?}", ringbuf), "RingBuf [0i, 1i, 2i, 3i, 4i, 5i, 6i, 7i, 8i, 9i]");
+        assert_eq!(format!("{:?}", ringbuf), "RingBuf [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]");
 
         let ringbuf: RingBuf<&str> = vec!["just", "one", "test", "more"].iter()
                                                                         .map(|&s| s)