Wait mode now catches KeyboardInterrupt.

In wait mode (-w), users can get annoyed and want their terminal back. It does so without the ugly stack trace.

The fortune of the commit (non-offensive):

    If a 6600 used paper tape instead of core memory, it would use up tape at about 30 miles/second.
                -- Grishman, Assembly Language Programming

Signed-off-by: Xiaomao Chen <xiaomao5@live.com>