* y2038 addon: Fix that check can never return True, add tests
At the beginning of `check_y2038_safe()` the variable `y2038safe` should
be initialized with `True` and only be set to `False` if there are any
issues. Otherwise it could never become `True`.
In the unit tests the return value of `check_y2038_safe()` is now
verified. But it does not yet work for the "good" example. The "good"
example also returns `False` since it finds warnings in the include
file. So this verification is marked with a "FIXME" comment.
* y2038 tests: Add "good" test file that does not use time functionality
The test file y2038-test-5-good-no-time-used.c does not use any time
functionality so the y2038 addon is not allowed to issue any warnings
and the check must return with `True` (code is safe).
Sebastian