Summary:
Passing std::atomic<uint64_t> variables to ASSERT_EQ()
results in compile error
C2718 'const T1': actual parameter with requested alignment of 8 won't be aligned.

VS2015 defines std::atomic as specially aligned type ( with 'alignas'),
however the compiler does not like declspec(align)ed  function
arguments.

Worked around by casting std::atomic<uint64_t> types to uint64_t
in ASSERT_EQ.
Closes https://github.com/facebook/rocksdb/pull/1450

Differential Revision: D4106788

Pulled By: yiwu-arbug

fbshipit-source-id: 5fb42c3