Enable quick info when hovering over function or =>

[ghost]

TypeScript Version: 2.7.0-dev.20171101

Code

foo(function() {});
foo(() => {});

Expected behavior:

We should be able to get quick info on the function without giving it a name.

Actual behavior:

Only way to get quick info is to add a name and hover over the name.

[mhegazy]

We should enable quickinfo on the function keyword, like we do with default today. possibly the => in the case of a lambda.

[mhegazy]

Duplicate of #2736