on ^C, clear current input line

When using `^C` with input on the line, the input is repeated and cursor position reset to 0. This is annoying when you use `^C` to ensure that you are on a clean prompt.

Before:

```bash
/ # somebadcommand^C
/ # somebadcommand
```

After:

```bash
/ # somebadcommand^C

/ # 
```