C level warnings not tested

[brodieG]

In particular, stuff like:

Warning: stack imbalance in '.Call', 178 then 177
Warning: stack imbalance in 'withVisible', 170 then 169
Warning: stack imbalance in '<-', 157 then 156
Warning: stack imbalance in '{', 154 then 153

Doesn't cause tests to fail, but probably should (at a minimum if it is different than when it was recorded, which presumably it almost always would be due to the protection stack level).