Fix T50736: Zero streaks in Glare node.

Fix T50736: Zero streaks in Glare node.

Please never, ever use same DNA var for two different things. Even worse
if they do not have same type and ranges!

This is only ensuring issues (as described in report, but also if
animating both RNA props using same DNA var... yuck).

And we were not even saving any byte in DNA, could reuse some padding
there to store the two new needed vars (yes, two, since we cannot re-use
existing one if we want to keep backward *and* forward compatibility).