up-to-date CAS function for android

Dear all,

There is CAS function modification for android:
 - Use *__sync_bool_compare_and_swap()* in "linux/JackAtomic_os.h" by default instead of *__atomic_cmpxchg()*.
 - For more detail, you can refer <A HREF="https://developer.android.com/tools/sdk/ndk/index.html">release note</A> of android-ndk-r7b version.
 - This changes available in JellyBean version or later.

Regards,
kimJeongYeon