Merging r366670 and r366694:

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r366670 | mantognini | 2019-07-22 11:39:13 +0200 (Mon, 22 Jul 2019) | 4 lines

[OpenCL] Improve destructor support in C++ for OpenCL

This re-applies r366422 with a fix for Bug PR42665 and a new regression
test.
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r366694 | mantognini | 2019-07-22 16:47:36 +0200 (Mon, 22 Jul 2019) | 5 lines

[NFC] Relaxed regression tests for PR42665

Following up on the buildbot failures, this commits relaxes some tests:
instead of checking for specific IR output, it now ensures that the
underlying issue (the crash), and only that, doesn't happen.
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llvm-svn: 366814