FPU rounding module

[Durchbruchswagen]

Implementation of the rounding module for FPU.

This module excepts that input is in normalized form (unless the number is subnormal) and, in accordance with RISC-V specification, detects tininess after rounding. The flag that allows generation of a rounding module that assumes that input was already rounded is to be used by modules that are able to perform both their operation and rounding at the same time (adder/subtractor, for example). In that case, this module only checks for errors and special cases (one of the inputs was inf/nan).