The trait will keep the `Iterator` naming, but a more concise module
name makes using the free functions less verbose. The module will define
iterables in addition to iterators, as it deals with iteration in
general.
Address issue #5257, for example these values all had the same hash value:
("aaa", "bbb", "ccc")
("aaab", "bb", "ccc")
("aaabbb", "", "ccc")
IterBytes for &[A] now includes the length, before calling iter_bytes on
each element.
IterBytes for &str is now terminated by a byte that does not appear in
UTF-8. This way only one more byte is processed when hashing strings.
I removed the `static-method-test.rs` test because it was heavily based
on `BaseIter` and there are plenty of other more complex uses of static
methods anyway.
