Clarify what iterating over operations means

[tobie]

In #494 (comment), @TimothyGu brought up the issue that operations have a many to one relationship with operation identifiers. That is, overloaded operations share a single identifier.

So when we say "iterate over the operations of interface |Foo|", what we really mean is something hand-wavy like: "iterate over the unique identifiers of the operations of interface |Foo| and consider the operations identified by a single identifier as a single but slightly special thing."

Do we need to be more specific, here?

[TimothyGu]

This issue is really only specific to the JS binding chapter. In a language like C++, the current system makes total sense.

Because #432 is still an open issue I’m not too worried about the handwaviness at this moment. We can of course define a new term to explain why uniqueness is a requirement for these iterations but it’s reasonably unambiguous w.r.t. what it means as it is.