Utilize fewer reexports

In regards to:

https://github.com/rust-lang/rust/issues/19253#issuecomment-64836729

This commit:

* Changes the #deriving code so that it generates code that utilizes fewer
  reexports (in particur Option::* and Result::*), which is necessary to
  remove those reexports in the future
* Changes other areas of the codebase so that fewer reexports are utilized

src/libstd/io/mod.rs

@@ -233,10 +233,12 @@ use int;
 use iter::{Iterator, IteratorExt};
 use mem::transmute;
 use ops::{BitOr, BitXor, BitAnd, Sub, Not};
-use option::{Option, Some, None};
+use option::Option;
+use option::Option::{Some, None};
 use os;
 use boxed::Box;
-use result::{Ok, Err, Result};
+use result::Result;
+use result::Result::{Ok, Err};
 use sys;
 use slice::{AsSlice, SlicePrelude};
 use str::{Str, StrPrelude};