Switch to purely namespaced enums

This breaks code that referred to variant names in the same namespace as
their enum. Reexport the variants in the old location or alter code to
refer to the new locations:

```
pub enum Foo {
    A,
    B
}

fn main() {
    let a = A;
}
```
=>
```
pub use self::Foo::{A, B};

pub enum Foo {
    A,
    B
}

fn main() {
    let a = A;
}
```
or
```
pub enum Foo {
    A,
    B
}

fn main() {
    let a = Foo::A;
}
```

[breaking-change]

1 files changed, 2 insertions, 0 deletions

diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index f30a4325eb8..2960c28a8b7 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -23,6 +23,8 @@
 //! instance, a walker looking for item names in a module will miss all of
 //! those that are created by the expansion of a macro.
 
+pub use self::FnKind::*;
+
 use abi::Abi;
 use ast::*;
 use ast;