Typing of instructions and programs should be uniform?

Right now instructions are typed against a stack, while programs are not:

`Inductive has_prog_type : program -> instr_type -> Prop :=
`

`with has_instr_type : instr -> stack -> instr_type -> Prop :=`

My opinion is that they should be typed the same way, and I lean towards both without a stack, but I think this needs more discussion.