uninitialized class properties allowed in strictNullChecks

[nippur72]

in strictNullChecks:

class Foo {
   someprop: string;
}
var a = new Foo();
a.someprop === undefined;

Expected behavior:
Do not allow to have someprop uninitialized, by requiring explicit initialization either directly or on the constructor.

Actual behavior:
no errors

[RyanCavanaugh]

Duplicate of #8476