Merging r155218:

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r155218 | rsmith | 2012-04-20 11:46:14 -0700 (Fri, 20 Apr 2012) | 5 lines

Fix bug where a class's (deleted) copy constructor would be implicitly given a
non-const reference parameter type if the class had any subobjects with deleted
copy constructors. This causes a rejects-valid if the class's copy constructor
is explicitly defaulted (as happens for some implementations of std::pair etc).

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llvm-svn: 156682