clib4

This is a fork of official clib2 present in adtools. The point of this
library is to make it Amiga OS4 only to maintain it easily and add all the
missing clib2 features that are difficult to add also on classic Amigas.
Classic Amigas has also ixemul that is the most complete, POSIX compliant,
library we have. It is a useless share code that most probably no one will
use. The goal is to try to make it POSIX compliant and fix also all the C++
problems we have with newer compilers. All warnings (except really few ones)
produced by GCC 10 and above are now gone.

All deprecated OS4 functions are replaced by modern OS4 one.

If you discover any issue, please let us know at:
https://github.com/AmigaLabs/clib4/issues