Fix Issue #3863 - jump-to-def goes to exports line.

When the result of jump-to-def looks like:
exports.foo = foo;

we now will try and jump-to-def on the rhs, as that's what the user most likely really wants.  Jumping to the exports line is rarely useful.

When we get the response for a jump-to-def, if it looks like we're jumping to a member expression like the example above, then we will grab the RHS, and trigger another jump-to-def on that, which should take us to the correct place.