Translation error of uses of the copysign family of functions

[keram88]

It appears clang translates calls to the copysign functions to the corresponding LLVM copysign intrinsics (such as @llvm.copysign.f32). This leads to failures when using the copysign functions and the fmod functions which also use copysign. See test/c/mathc/copysign.c for a failing example.