Workaround a bug in double-wide intrinsics of Clang/x64 with ASan enabled

Workaround a bug in double-wide intrinsics of Clang/x64 with ASan enabled

As of clang-3.8, double-wide arguments are incorrectly passed to
atomic intrinsic operations for x64 target if Address Sanitizer is
enabled.

* src/atomic_ops.h [__has_feature(address_sanitizer)]
(AO_ADDRESS_SANITIZER): New internal macro.
* src/atomic_ops/sysdeps/gcc/x86.h [AO_GCC_ATOMIC_TEST_AND_SET
&& __clang__ && __x86_64__ && !__ILP32__]
(AO_SKIPATOMIC_double_compare_and_swap_ANY, AO_SKIPATOMIC_double_load,
AO_SKIPATOMIC_double_load_acquire, AO_SKIPATOMIC_double_store,
AO_SKIPATOMIC_double_store_release): Define also if AO_ADDRESS_SANITIZER;
update comment.