simu - remove "save" and "restore"
ex 5.21 - using lower abstraction
file renamed

file name for patches are changed since the change has
something more than just list primitives,
I find it's more comfortable to say that we are actually
"switching to a lower abstraction" so some primitives in the original
design becomes the result of composition of lower primitives.
listprim2 -> lower

list primitives *and stack primitives*
5.3.2 - some notes after implementing this system
reference
+TODO: work with legacy system
simu - changing a pred name a little bit
legacy - new const handling & reserve regs
simu - remove unnecessary imports
legacy - redo machine initialization
need some concerns about tracking modified insn
legacy - pointer support and more
ex 5.21 - legacy lower done