clib2 Code

- Getting ready for a new release...

- <sys/types.h> now also includes <time.h> and <stddef.h>.

- The socket/usergroup API function and data type definitions that used to
be defined in <unistd.h> have been moved into a separate header file
<sys/clib2_net.h> which, for backwards compatibility, can be include
from within <unistd.h> if the preprocessor symbol __USE_CLIB2_NETLIB
is defined early on. Eventually, <sys/clib2_net.h> should be removed
from the general header files and become a local library build header
file altogether. Note that in this case you would have to build your
own software using common TCP/IP SDK header files.

- The thread-safe version of isatty() should now work for stdio
file descriptors, too.

- Retrofitted thread-safety into the termios code.

- Added some documentation on the skeleton library code.

- Added a complete shared library skeleton example to demonstrate how the
clib2 shared library initialization/cleanup functions should be used.
This is a dual-build library which will both work with the plain 68k
AmigaOS and the PowerPC native AmigaOS4. The example source code can be
found in the "skeleton_library" subdirectory.

- Fixed an important error in the documentation...

- Added the clib2 shared library initialization/cleanup code.

- Modified to build with the thread-safe library on OS4.

- Updated to use the proper OS4 build environment.