Squash me.
Merge me length
Tweaks in @safe and nothrow qualifiers
Support for narrow strings in cycle static array

In case anybody wanted to implement a circular buffer on unicode text.

The cycle is read-only, so of limited use, but that doesn't mean we shouldn't support it.
Merge me
merge me string
Added specialized version for cycle!(T[1u])

Because someone may want a cycle of a single element, in particular, things like recurrence do this.

Also note making it an alias of Repeat is not acceptable, because repeat carries the element internally, whereas cycle references external data.