clib2 Code

- Fixed the header files I broke by mistake.

- You can now request that your program uses the clib2 alloca() function
rather than the built-in compiler alloca().

- alloca() is now part of libunix.a, too.

- Added notes on where to find documentation and updates to each header file.

- In libunix.a malloc(), calloc() and realloc() no longer treat a
request to allocate 0 bytes as an error, returning NULL. They all
return a pointer sized memory chunk (= four bytes) initialized to
NULL (= 0) instead.

- The alloca() implementation which allocates memory from the system
rather than the local stack frame is thread-safe now. It also
interacts with the realloc(), calloc(), free() and malloc() functions
in that the alloca() cleanup routine is called once alloca() has
done its job. If all the memory allocated through alloca() has been
released no further calls to the cleanup function will be made.

- In the thread-safe library, realloc() permitted two different overlapping
calls to succeed in trying to reallocate the same chunk of memory due to
a race condition. Fixed.

- Moved the thread-safe library documentation.

- The malloc() in libunix.a now allocates four bytes of memory instead
of just one for a request to allocate 0 bytes.

- Corrected the section numbering.

- Fixed the remaining HTML errors.

- Changed the assertion message text shown in the requester window.

- The standard malloc() now sets errno to EINVAL for zero length
allocations.

- Updated the general documentation and started to document the implementation-specific
behaviour of the library functions.

- In libunix.a malloc(), calloc() and realloc() no longer treat a
request to allocate 0 bytes as an error, returning NULL. They all
return a 1 byte memory chunk initialized to 0 instead.

- Replaced the sqrt() call.