K 10
svn:author
V 2
ed
K 8
svn:date
V 27
2012-08-31T22:22:14.840547Z
K 7
svn:log
V 342
Properly enable Clang-style atomics when available.

In addition to testing against cxx_atomic, we must check c_atomic. The
former is only set when building C++ code. Also use __has_extension
instead of __has_feature. This allows us to use the atomics outside of
C11.

Reported by:	Ariane van der Steldt <ariane stack nl>
PR:		threads/170073

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