Get rid of isInfinite()?

[Mehrdad]

I feel like isInfinite is useless for typical cases... the only 
"infinite" (perhaps I should call it "unbounded" instead?) range 
I've ever realistically come across is a stream, like console 
input or a network stream.

Of course, isInfinite doesn't make any sense for any type of 
wrapper around console input -- is it true or false?
You can't tell, because it depends on whether the input is 
redirected.
If the console input was redirected, then it would be finite, 
with a certain length (the length of the file).
If not, then it would be infinite (er, unbounded).

So IMHO, we should deprecate isInfinite entirely, and instead 
rely on length being size_t.max.

Not only would it make more sense, but it would make it possible 
to create a random-access wrapper around an input range (like 
console input), which lazily fetches its data.
Then you can work with console input like a regular string!