RISC-V: Generic <math.h> and soft-fp Routines

RISC-V: Generic <math.h> and soft-fp Routines

This patch contains the miscellaneous math routines and headers we have
implemented for RISC-V.  This includes things from <math.h> that aren't
completely ISA-generic, floating-point bit manipulation, and soft-fp
hooks.

2018-01-29  Palmer Dabbelt  <palmer@sifive.com>

        * sysdeps/riscv/bits/fenv.h: New file.
        * sysdeps/riscv/e_sqrtl.c: Likewise.
        * sysdeps/riscv/fpu_control.h: Likewise.
        * sysdeps/riscv/math-tests.h: Likewise.
        * sysdeps/riscv/nofpu/Implies: Likewise.
        * sysdeps/riscv/sfp-machine.h: Likewise.
        * sysdeps/riscv/tininess.h: Likewise.