Allow handling of user interrupts (ctrl-C)

If enabled, readline will throw `UserInterruptException` when the user types the interrupt (ctrl-C) character. This is currently only supported on Unix terminals and is accomplished by disabling TTY handling of the interrupt character.

*Original Feature Request*: It would be nice if `ConsoleReader.readline()` could handle ctrl-C by returning immediately and signaling this to the application (possibly by throwing an exception). This needs to be distingishable from EOF / ctrl-D (which returns `null`) and the user entering a blank line by simply pressing enter. Applications that handle multi-line input typically respond to ctrl-C by clearing the multi-line input state. For example, the user can enter a SQL query over multiple lines and press ctrl-C to abort and start typing a new query.