[PATCH] [libc++] Support Newlib as libc++'s C library [cmath part, part 2]

[JF Bastien]

I looked at this again, and it seems like they should be in newlib because of C99. Should this be fixed in newlib instead?

There was a thread about this on the newlib mailing list:
  https://sourceware.org/ml/newlib/2014/msg00349.html

These two functions are mentioned later.

http://reviews.llvm.org/D5420