Added a workaround for clang 3.4 bug: the compiler does not implement __atomic intrinsics even though it defines __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 macro.
Removed incorrect constexpr qualifications from constructors with non-empty bodies.
Added missing fence functions for the clang 3.4 workaround. Also made atomic_flag copy and assignment to be deleted on C++11 compilers.
Attempt to make Darwin clang compile the asm statement.
Further attempts to work around clang compilation failures.
Further attempts to work around clang bugs.
Merge branch 'develop'