clib2 Code

- Added a comment to clarify which version number is being used for the
'_fd' data structure definition.

- Added functions which modify the callback function and the userdata pointer
stored in a low level unbuffered file/socket data structure. These function
perform the proper locking and are thus safe to use in a thread-safe environment.

- The low level unbuffered file/socket now has a public equivalent, which
is defined (along with the typedefs and flags) in <sys/clib2_io.h>. Functions
for tinkering with it are still to come.

- The math kernel code no longer uses its own private scalbn() function.

- Added a function prototype for the _exit() function. Note that _exit() is
not an ISO 'C' function.

- Corrected the getopt() function prototype, as prompted by Henning Nielsen Lund.

- Added a directory to hold contributed code which has not been integrated
with the library yet.

- The byteswap code was contributed by Peter Bengtsson. Thank you very much!

- The printf() family no longer adds a 0 or 0x prefix if the alternate
conversion modifier is present for the %o and %x conversions and the
value to be converted is 0 already. Put another way, printf("%#x %#o",0,0);
now prints "0 0". This required another change so that %p always includes
the 0x prefix even if the pointer involved is a NULL pointer.

- readlink() no longer sort-of-works for files and directories. It now only
works for soft linked objects and returns an error for everything else.
This is based upon a fix by Peter Bengtsson. Thank you very much!

- Moved the lstat() local Lock() function into its own separate file.

- uname() now returns correct and robust information for OS version
numbers > 36. This integrates a fix by Peter Bengtsson. Thank you
very much!

- Moved the crtbegin.o/crtend.o files out of the link libraries. Moving
them in was intended to work as a fix for the shared library build, but
now it seems that this has to be done at the link stage through the
GCC specs file...

- Integrated a fix for __rem_pio2() which affects sin(), tan() and cos(),
contributed by Steven Solie. Thank you very much!

- The internal 'struct fd' file descriptor table entry data structure
now has a user data field entry.

- Rearranged the contents of the 'struct fd' file descriptor table entry
data structure in preparation for making it public. Also added a version
field so that user code can handle changes to it gracefully. The default
file is no longer a BCPL pointer to a file handle by default, but
both a BPTR and a socket identifier, wrapped into a union.

- Added experimental tilde expansion in Unix path names. This still needs
some more work.

- Removed an unnecessary (STRPTR) cast.