Bug 15327 – -cov should not mark `assert(0)` (and ideally paths leading unconditionally to it) as uncovered

`assert(0)` is almost always used as a "waveguide terminator" to mark paths that, if ever reached, mean there's a bug in the code. Consequently, the `assert(0)` lines and all paths leading to them cannot and should not ever be covered. Currently such lines are marked with 0000000 and gratuitously degrade the coverage ratio of legitimate code. A simple fix would be to not mark `assert(0)` lines as uncovered (also `assert(false)` etc). That would be enough to close this issue. A more sophisticated approach would also do the same with code leading up to the `assert(0)`.

*** This issue has been marked as a duplicate of issue 14855 ***