Don't replace lazy arrays with the reference backend's immediates.
Don't replace lazy arrays with the reference backend's immediates.

This fixes a bug that we'd otherwise introduce by coalescing small arrays.
Under certain circumstances, the class of the cached array could be changed
to the 'simple-immediate' class of the reference backend.  This, in turn,
would wreak havoc unto every code that would later reference that
particular constant.

marcoheisig/Petalisp,marcoheisig/Petalisp