clib2 Code

- Added __set_h_errno() and __get_h_errno() functions.

- The thread-safe library now tries to enable bsdsocket.library base
sharing and attempts to make the TCP/IP stack call the local
__set_errno() and __set_h_errno(), so that any Process calling
the library functions will get a chance to see proper error
codes. Whether any of these features could be enabled can be tested
through two global variables __can_share_socket_library_base and
__thread_safe_errno_h_errno which are defined in <dos.h>. Note that
for both features to work you will need the Roadshow bsdsocket.library
version 4.275 or higher.

- Corrected a variable name.

- Updated the build files so that atanh() and atanhf() are built for the
respective math libraries.

- Implemented atanh() and atanhf() which were not listed in the TODO
file but were still unimplemented up until now.

- Replaced ldexp() and modf().

- Corrected a typo.

- Updated math_hypot.c to a newer (e_hypot.c 1.3 95/01/18) version from
fdlibm which uses macros for manipulating the high and low words of a
double, like the rest of fdlibm functions in clib2. The previous version
would give bogus results when compiled with -O3 in clib2 which lead to
"interesting" results (and lots of fun while searching for the problem)
in Ghostscript. Wish I managed to track this down yesterday for 1.196
release... <aantonijevic>

- Removed <sys/clib2_net.h> and every reference to it.

- Removed the compiler log file generation.

- Removed a couple of compiler warnings; fishing for more...

- Updated the thread-safe library documentation section.