Merging r277522:

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r277522 | dcoughlin | 2016-08-02 14:07:23 -0700 (Tue, 02 Aug 2016) | 8 lines

[CFG] Fix crash finding destructor of lifetime-extended temporary.

Fix a crash under -Wthread-safety when finding the destructor for a
lifetime-extending reference.

A patch by Nandor Licker!

Differential Revision: https://reviews.llvm.org/D22419
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llvm-svn: 278376