std: Stabilize std::fmt

This commit applies the stabilization of std::fmt as outlined in [RFC 380][rfc].
There are a number of breaking changes as a part of this commit which will need
to be handled to migrated old code:

* A number of formatting traits have been removed: String, Bool, Char, Unsigned,
  Signed, and Float. It is recommended to instead use Show wherever possible or
  to use adaptor structs to implement other methods of formatting.

* The format specifier for Boolean has changed from `t` to `b`.

* The enum `FormatError` has been renamed to `Error` as well as becoming a unit
  struct instead of an enum. The `WriteError` variant no longer exists.

* The `format_args_method!` macro has been removed with no replacement. Alter
  code to use the `format_args!` macro instead.

* The public fields of a `Formatter` have become read-only with no replacement.
  Use a new formatting string to alter the formatting flags in combination with
  the `write!` macro. The fields can be accessed through accessor methods on the
  `Formatter` structure.

Other than these breaking changes, the contents of std::fmt should now also all
contain stability markers. Most of them are still #[unstable] or #[experimental]

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0380-stabilize-std-fmt.md
[breaking-change]

Closes #18904

src/librustdoc/lib.rs

@@ -168,11 +168,11 @@ pub fn main_args(args: &[String]) -> int {
     if matches.opt_strs("passes").as_slice() == &["list".to_string()] {
         println!("Available passes for running rustdoc:");
         for &(name, _, description) in PASSES.iter() {
-            println!("{:>20s} - {}", name, description);
+            println!("{:>20} - {}", name, description);
         }
         println!("{}", "\nDefault passes for rustdoc:"); // FIXME: #9970
         for &name in DEFAULT_PASSES.iter() {
-            println!("{:>20s}", name);
+            println!("{:>20}", name);
         }
         return 0;
     }