[phobos] Silent failure of std.container unittests

[Sean Kelly]

Walter's change fixed the issue where non-throwing asserts weren't triggering a unittest failure, but it also reverted my change to trap unhandled exceptions, set a "fail" flag, and continue with the next test.  I'd fix this, but what I'm confused about is why the support-non-throwing-asserts change was re-added in the first place.  So instead I'd like to ask what the eventual/intended/desired/whatever behavior is for unit tests so I can work towards that.  I'd like throwing asserts and for each unittest in a module to be run separately so recovery from an AssertError (which I'd like for unit tests) is at the granularity of the unittest block, not the module.  The best I can do without a compiler change is module-level granularity like we have now, but asserts could all throw again, etc.  Should this be an intermediate step?  Should we keep non-throwing asserts?  Halp plzz.