rpn.hs: simplify

Use `and` instead of `all (==True)`.
Also, remove unnecessary type signature for `read termStr`.
rpn.rb: raise error on unexpected operator application
rpn.hs: rename `f` to `stackManip`

No functional change.
rpn.hs: match ruby version's `c` variable
rpn.rb: use `shift` instead of `reverse` + `pop`