'Smarter' keyframing tools ('needed' option for manual and auto keyframing)
now work better than before, with more cases handled in an predictable
manner. There are still a few cases it still doesn't handle well yet. Those will be
fixed in the next few days.
See comments in code for rules in place now. Also, I've changed the code
to use the IS_EQ macro instead of my clumsy sqrt((a-b)*(a-b)) calculations.
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