oceani: differentiate static-sized arrays from others.

Some arrays will always have the same size - a static size.
Others might have a different size each time their scope is entered, if
the size is calculates from a variable.

The latter need to be reallocated whenever scope is entered, the former
do not.

This will matter when we create call frames to be able to handle
recursion.

So detect and handle the difference now.

Signed-off-by: NeilBrown <neil@brown.name>