TypeScript import(...) types

TypeScript 2.9 will support a new `import("foo")` syntax for referencing types in modules which have not been imported. See the original pull request at https://github.com/Microsoft/TypeScript/issues/14844 for more details.

To support this, Babel will likely need to implement

- [x] Parsing support
- [x] Emit support