recursive equal, and firstDifference functions

[timotheecour]

> somewhere else, but I don't see a relevant package. Maybe a new 
> std.algorithm2 for non-ranges?
>
> Also, the OT's firstDifference would go there too, and I have a 
> recursive (to specified level) toStringRecurse that would 
> belong there too.

Also, I'd add to that list copyRecurse and some more, that 
operate on arbitrary types, not just ranges, so we have:

equalRecurse
copyRecurse (deep copy)
toStringRecurse
firstDifference (see OT)
toHashRecurse (should compare equal with a data structure 
serialized and then deserialized via a serialization function, eg 
std.orange)

I'm sure there's more.

that seems a starting point for a new package that operates on 
any type recursively (not just ranges), no?
std.deep?std.recurse?
Some of those could have a depth level compile time parameter 
that stops recursion at that level, which would be infinity by 
default.