clang + libc++ + c++17 errors

[yasushi-saito]

"using namespace std;" in farmhash.cc causes the following error:
you should remove the "using namespace std" from the source code.

lib/hash/farmhash.cc:2006:14: error: reference to 'data' is ambiguous
memcpy(data + i, &u, 1); // uint8_t -> char
^
lib/hash/farmhash.cc:1990:13: note: candidate found by name lookup is 'data'
static char data[kDataSize];
^
/scratch-nvme/saito/bazel/_bazel_ysaito/e1a7c710473372ee150f48ad758734b2/external/grail_toolchain/include/c++/v1/iterator:1876:22: note: candidate found by name lookup is 'std::__1::data'
constexpr const _Ep* data(initializer_list<_Ep> __il) noexcept { return __il.begin(); }