IDLE currently ignores the indent width setting in the
main shell window, and forces it to use tab characters,
8 spaces wide.  This is ugly, and causes problems when
you write code in the shell and then cut-and-paste it
into a real editor window.

This patch adds an option (off by default) to honour
the indent width setting in the PyShell window rather
than using tabs.  This makes it much nicer to edit
commands that use several levels of indenting.  

The only reason for this to be an option, and for it to
be off by default, is that it looks a little weird when
the second line of code is indented, but still lines up
with the first indented line because the prompt is also
4 characters wide.  Fixing it so this would not look
weird would be nice, but would require a lot of Tk
hacking and might make the gui slower.