Skip ;; even on a separate line (fixes #259)

[mattiase]

This allows repeated tuareg-eval-phrase to execute phrases in sequence without the user needing to do anything in-between.

[mattiase]

This PR is conservative to avoid unintended consequences. For instance, comments before the ;; still prevents the latter form being skipped over:

let _ = 1 (* comment *) ;;

or

let _ = 2
(* comment *)
;;

These cases seem to be rare.

[Fourchaux]

Well done. Thank you very much. :smiley:

The ( comment ) ;; are indeed very rare.

[Chris00]

Thanks.