Merging r279008:

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r279008 | marshall | 2016-08-17 16:24:02 -0700 (Wed, 17 Aug 2016) | 1 line

make the associative containers do the right thing for propogate_on_container_assignment. Fixes bug #29001. Tests are only for <map> right now - more complete tests will come when we revamp our allocator testing structure.
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llvm-svn: 279017