Merging r270884:

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r270884 | jlpeyton | 2016-05-26 13:19:10 -0500 (Thu, 26 May 2016) | 11 lines

Make LIBOMP_USE_ITT_NOTIFY a setting that can be enabled or disabled

On Blue Gene/Q, having LIBOMP_USE_ITT_NOTIFY support compiled into a
statically-linked binary causes a failure at runtime because dlopen fails.
This patch changes LIBOMP_USE_ITT_NOTIFY to a cacheable configuration setting
that can be disabled.

Patch by John Mellor-Crummey

Differential Revision: http://reviews.llvm.org/D20517

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llvm-svn: 271581