Establish a proper prototype chain

[silkentrance]

Given the following input source

class A

class B extends A


console.log A.isPrototypeOf B

yields false

whereas the same using babel

class A {}

class B extends A {}

console.log(A.isPrototypeOf(B));

yields true.

See also node prototype chain is broken.

[GeoffreyBooth]

Returns true in 2.0.0-beta1.