This change makes all non-user-creatable structures non-comparable. This
makes it easier to add changes later that don't introduce breaking
changes from the go compatibility guarantees perspective.
This, of course, implies that this change _is_ a breaking change, but since
these structures are not intended to be created by users (or de-referenced),
it should be okay.
This change:
* Gets rid of the `.toC()` functions for Options objects, since they
were redundant with the `populateXxxOptions()`.
* Adds support for `errorTarget` to the `RemoteOptions`, since they are
used in the same stack for some functions (like `Fetch()`). Now for
those cases, the error returned by the callback will be preserved
as-is.
lhchavez