C#: Update PreSSA to reference the new use-use predicates.

[aschackmull]

This adds a few tuples to the updated predicates. Spot-checking the additions for adjacentReadPairSameVar all look correct. The differences for getAFirstRead all had to do with ref variables, and I couldn't quite make sense of them, but there weren't that many, and I think the new version ought to be more correct.

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[hvitved]

LGTM (but let's wait for DCA to come back clean before merging).

[aschackmull]

Dca looks fine. I checked the single new alert - it's technically true, the assigned value is never read, but it relies on knowing that a foreach statement executes at least once, so I don't think it can be removed. In any case, this just shows that we just got a very minor tweak to the CFG splitting, but the useless assignment query ought possibly not make use of splitting information, since the compiler will likely insist on keeping the initialisation.