* Avoid a crash with `@typedef` in a script file.
Scripts (as opposed to modules) do not have a symbol object. If a script
contains a `@typdef` defined on a namespace called `exports`, TypeScript
crashes because it attempts to create an exported symbol on the
(non-existent) symbol of the SourceFile.
This change avoids the crash by explicitly checking if the source file
has a symbol object, i.e. whether it is a module.
* Add usage of exports.SomeName typedef.
* Fix bug at bind site rather than in declare func
