* `list->array' now accepts an optional shape argument, and always returns
an immutable array
* `vector->array' now accepts an optional shape argument, and always
returns a mutable array
* Removed `make-mutable-array' because `vector->array' does its job now (I
never liked the name anyway)
* Renamed `unsafe-mutable-array' to `unsafe-vector->array'
* Added optional type annotation to `array' macro to match `mutable-array'
* Reworded error messages in array broadcasting functions
* Made minor array doc fixes