[Proposal] Additional operator overloadings for multidimentional indexing and slicing

[bearophile]

David Nadlinger:

> Actually, I'd say its the other way round – opDollar rather 
> corresponds to opDoubleEqualSign, as it simply describes the 
> character used.

I agree. It's the opposite of the semantic names of the original
operator overloading set.

Bye,
bearophile