[libcxx] Multiple function declaration conflicts

Hi,
I'm trying to build library via MS toolset with fresh compiler (November 2013 CTP).
I have several errors:

"function declaration conflicts with introduced by using declaration" (conflicts with MSVC RT)

example in libcxx cmath header:

inline _LIBCPP_INLINE_VISIBILITY
double
abs(double __x) _NOEXCEPT {return fabs(__x);}

Questions:

1.According to C++1x Standard the MSVC have not full implementation?
(That is cause this error, and doubled declarations should be avoided?)

2. Or such errors should be avoided via namespace kung-fu?

3. I need fill a bug?

Thanks,
       Michael.