closing out Library*NegativeTest issue and adding comments

Updates language.status to reflect the invalid status of issue #354.  Also adds comments to the test cases to help clarify their intended behavior for future readers.

Committed: https://code.google.com/p/dart/source/detail?r=3202

[jimhug, 2012-01-11 18:42:05]

Hi Siva,

I'm trying to ensure a clean resolution to the library negative tests confusions
we had yesterday.  This commit should just update the status file to remove the
concerns about the now invalid test bug and should update the test cases
themselves only by adding comments to help explain the intended purpose of the
test.  Can you please take a look at this and verify both that I'm not breaking
these tests and that the comments accurately reflect the tests?

Thanks! - Jim

[siva, 2012-01-11 19:23:57]

lgtm