currently space is still acting as a sort of memory manager.
For proper linking, all objects must be reachable from space, hence the plural versions like messages and addresses (even they are instances, it is the list that is important)
To dish out instance to use, the head must be kept, ie next_XXX for intergers, return addresses and messages
Since integers are first class objects, we need to use an integer object
as the return address. The actual address can not be stored in an
instance variable since it is not an object.
The address is unique to the label and never changes after positioning
(using the int is next up)
rather use builder in two ways, than sometimes compiler and sometimes
builder
Also makes it possible to reuse builtin code in mom’s to_risc, as both
use builder. The builtin code by directly adding to compiler, the mom
code not.
slot >> reg makes sense, being a slot_to_reg
but . . .
consistently use of << (as meaning assignment , =) also makes sense
allow both and let time tell which makes more sense
