Allow import/export of libraries with no name.

Allow import/export of libraries with no name.

BUG=http://dartbug.com/11475
R=kasperl@google.com

Committed: https://code.google.com/p/dart/source/detail?r=28049

Committed: https://code.google.com/p/dart/source/detail?r=28079

[kasperl, 2013-09-30 11:43:49]

LGTM. Do we still fail if we try to import a part (marked with 'part of') and is
that covered by tests?

[Johnni Winther, 2013-09-30 12:15:32]

On 2013/09/30 11:43:49, kasperl wrote:
> LGTM. Do we still fail if we try to import a part (marked with 'part of') and
is
> that covered by tests?

We check it, but I'm not sure we have a test for it. Will look at it in another
CL.

[Johnni Winther, 2013-09-30 12:18:34]

Committed patchset #1 manually as r28049 (presubmit successful).

[Johnni Winther, 2013-10-01 08:35:06]

Committed patchset #2 manually as r28079 (presubmit successful).