* include/bits/atomic_base.h (__atomic_flag_base): Define _M_i
        based on the value of __GCC_ATOMIC_TEST_AND_SET_TRUEVAL.
        (ATOMIC_FLAG_INIT): Initialize with 0, not false.
        (atomic_flag::atomic_flag): Use __GCC_ATOMIC_TEST_AND_SET_TRUEVAL.

From-SVN: r183582