Merge a couple of documentation changes.
Merged revisions 56988-56989 via svnmerge from
https://svn.boost.org/svn/boost/trunk
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r56988 | danieljames | 2009-10-18 21:18:28 +0100 (Sun, 18 Oct 2009) | 1 line
Add release notes for unordered.
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r56989 | danieljames | 2009-10-18 21:18:43 +0100 (Sun, 18 Oct 2009) | 1 line
Mention that image attributes are supported.
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