Mathematic library service

We also add mathematic functions to ease the portability of third-party code. These functions were imported from the NetBSD^7.1 project. It provides all necessary functions to perform math operations (sqrt(), ...).

To enable the libmath functions, you must define the maccro POK_NEEDS_LIBMATH.

To have the complete list, please refer to the libpok reference manual available on each POK release. A list of these functions is also available in this document, in chapter 8.