[IronPython] Console history

[Sanghyeon Seo]

This is my pet peeve. This applies to both 1.1 and 2.0a1.

1. Run ipy.exe with -X:TabCompletion.
2. Execute a line. (Let's say "a = 1".)
3. Press up arrow. (The last line appears.)
4. Press down arrow. (The line stays.)

What I want:

4. The line disappears.

Otherwise, you're forced to delete the entire line, when you thought
you'd edit one of the line in history, and changed your mind. The idea
is that down arrow should reverse the any effect up arrow had.

This is the case for any readline-based systems like Linux bash shell
and CPython installs on Unix. This is not the case for Windows cmd.exe
and CPython installs on Windows though.

-- 
Seo Sanghyeon