TAB line position snafu

[Barry Warsaw]

revno 717

First, thanks for fixing the point-position-in-line issue when re-indenting a line. It's working great except for one small problem. Take this code:

def keywords(**keywords):
    if 'utf8_strings' in keywords and is_py3:
            del keywords['utf8_strings']
    return keywords

Put line at column 0 of the `del` line and hit TAB. Point ends up on the 'y' of `is_py3` on the previous line. You just have to make sure that when re-indenting a line, point doesn't end up going negative (i.e. past the left edge of column 0).