[giow] (0) Define structured cloning for Map and Set
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=23892
Affected topics: DOM APIs, HTML

git-svn-id: http://svn.whatwg.org/webapps@8374 340c8d12-0b0e-0410-8428-c7bf67bfef74