Increment a python floating point value by the smallest possible amount
<p>I'm using floating point values as dictionary keys.</p>

<p>Occasionally, <em>very</em> occasionally (and perhaps never, but not certainly never), there will be collisions. I would like to resolve these by incrementing the floating point value by as small an amount as possible. How can I do this?</p>

<p>In C, I would twiddle the bits of the mantissa to achieve this, but I assume that isn't possible in python.</p>
