add native ("...") class syntax to bind native class (#152)

First implementation of #152.

Note that this feature supports neither lazy loading nor load error handling, while the current JSX compiler loads JS modules (source-map and esmangle) dynamically. Should we support such features?

FYI, if I load esprima, esmangle, escodegen and source-map first, it takes 60 ms. on my MacBook Air.