Merging r276900:

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r276900 | epilk | 2016-07-27 11:25:10 -0700 (Wed, 27 Jul 2016) | 5 lines

[Sema] Teach getCurrentThisType to reconize lambda in in-class initializer

Fixes PR27994, a crash on valid.

Differential revision: https://reviews.llvm.org/D21145
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llvm-svn: 278374