Merging r353431:

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r353431 | stulova | 2019-02-07 18:32:37 +0100 (Thu, 07 Feb 2019) | 9 lines

[OpenCL][PR40603] In C++ preserve compatibility with OpenCL C v2.0

Valid OpenCL C code should still compile in C++ mode.

This change enables extensions and OpenCL types.

Differential Revision: https://reviews.llvm.org/D57824


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llvm-svn: 353826