Scope of a var in catch is catchclause

A `var` that is declared in catch clauses should have the scope that the try/catch is in, but instead `.scope` returns a scope that is the catch clause itself.

For example, this code:

```
var recast = require("recast");
var types = require("ast-types");

var ast = recast.parse(`
function f() {
try {
var a = 4;
} catch (e) {
var b = 3;
}
}
`);

types.visit(ast, {
visitVariableDeclarator: function(path) {
var name = path.node.id.name;
var scope = path.scope;
console.log(name, scope.node.type, scope.declares(name));
scope = scope.parent;
console.log(name, scope.node.type, scope.declares(name));
return false;
}
});
```

Outputs this:

```
a FunctionDeclaration true
a Program false
b CatchClause false
b FunctionDeclaration true
```

But I think it should output this:

```
a FunctionDeclaration true
a Program false
b FunctionDeclaration true
b Program false
```

Reproduce the supplied example with recast and ast-types, then trace the visitVariableDeclarator entry point and inspect path.scope for declarations inside the CatchClause. Done means the example reports b as declared by the FunctionDeclaration and its parent as Program, matching the expected output.

Written by the indexing model from the issue text.