COMPILER:remove unused params; DO NOT WORK

It removes unused params
`function f(a){return 0}` becomes `function f(){return 0}`
`function f(a,b){return b}` is not changed
`function f(a,b){return a}` becomes `function f(a){return a}`

It doesnt not work (because of `caml_call_gen` i suppose)
Is there a way to make this optim work ? otherwise, just ignore and close this PR