clib2 Code

- raise() no longer resets the signal handler before it invokes the one
currently configured. It merely blocks the delivery of the respective
signal to prevent recursion.

- raise() now drops into abort() if a signal handler is set to
SIG_DFL. The exception is in SIGINT delivery, which has the
effect of printing a different termination message but otherwise
program flow takes the same path as abort().

- Moved the signal block mask and the signal function table out of
signal_data.c and into signal_raise.c where they are actually used.
This makes it possible to override the default definition of the
__check_abort_enabled variable in your own programs.

- The name of the public record locking semaphore has to be preallocated
for OS4 if the AllocSysObject() function is used to create it.

- Updated the specs file not to reference the main.o files any more.

- Clarified the caveats of the libm.a use.

- Ready for release...

- Oops, nearly broke fcntl() again for sockets.

- Small fixes to fcntl() and select() to cover the thread-safe
fd->fd_DefaultFile == ZERO case.

- Added a description of the thread-safe stdin/stdout/stderr behaviour.

- Activated the dormant thread-safe standard input/output/error
handling code.

- The thread-safe system() call now blocks all standard I/O operations
until the function has returned. Which is harsh, but there is no
elegant solution to the issue of keeping the same dos.library
file handles from concurrent use which SystemTagList() might just
end up using.