These messages are used by console frontends to check whether the
current input is complete or not. If it is not complete, the next line
is treated as the continuation of the code, and a '...' prompt is used
to show that.

To provide support for qtconsole, I have made it such that IHaskell
always responds to an is_complete_request by saying that the code is
complete, which only allows for single line inputs.