When compiling code like this:
x = { foo: x }
We don't want to put a new JS::Object in `x` until *after* we've
evaluated `x` for the `foo` field.
This fixes an issue when loading https://puter.com/ :^)
In case of {get func() {}, set func() {}} we were wrongly setting the
function name to 'func' and then later trying to replace an empty name
with 'get func'/'set func' which failed.
Instead, set the name to 'get func'/'set func' right away.
The code in put_by_property_key is kept, for when that is called
by put_by_value.
