Implementations of copysign[f], frexp[f], logb[f], and modf[f] are added.
Reviewers: asteinhauser
Differential Revision: https://reviews.llvm.org/D81134
A new utils library named 'fputil' is added. This library is used in
math tests and the MPFR wrapper. The math implementations will be
modified to use this library in a later round.
Reviewers: phosek
Differential Revision: https://reviews.llvm.org/D79724