in untyped mode, emit no types near arrow functions

[evmar]

Emitting a type for arrow functions triggers ASI due to
the newlines in the JSDoc type annotation. Fix this by just
skipping type annotations.

Works around issue #57.

[evmar]

Maybe I should just always skip arrow functions even in typed mode, 'cause we can't get the annotations right... what do you think?

[rkirov]

LGTM, since we agreed to work towards turning off annotations for untyped, #59 and this is going in that direction.

For typed mode I think we have to fix this proper, how about adding extra parens?

function foo() {
    return (
/**
 * @param { string} x
 */
(x: string) => 3
);}

It does trigger the double emit bug, but at least it preserves the meaning of the original code.