Move to new line if any exception occurs

[judah]

Currently if the Settings enable the sigINT handler, then when control-C is pressed we move to the next line.

We should probably allow more exceptions than just that -- for example:

• darcs has its own ctrl-c catcher
• ghc installs its own ctrl-c handler which is easy to use in 6.10

I'm a little wary of handling all exceptions this way, since the cleanup code might cause the exception to be re-thrown.

Either we could:

• Allow any exception to trigger a move past
• Let the programmer set the allowable exceptions in the Settings.

[judah]

Done; all exceptions cause us to move past the input line.

If an error is thrown by the cleanup code, then it's probably the same kind of error (e.g., EOF) that was trapped in the first place. Furthermore, since all we're doing is writing to the terminal, if an error occurs the program would have been hard-pressed to report it anyway.

So I don't think this should cause a problem in practice.