clib2 Code

- Corrected a typo in the OS4 destructor code.

- Added S_IREAD, S_IWRITE and S_IEXEC aliases to <sys/stat.h>.

- Reimplemented the constructor/destructor invocation code for GCC.
Both the 68k and PowerPC platform now invoke them in the same order
and the 68k code uses the designated invocation priorities. The
PowerPC destructor function now sets up the exit() jmp_buf before
the destructor functions are called.

- Reworked the constructor/destructor macros again.

- Cleaned up the GCC constructor/destructor macros again. There is more to come.

- Thanks to Joerg Strohmayer, the GCC library build now manages to
invoke the library's constructor/destructor functions in a
very particular order. That way, you can use constructor/destructor
functions in your own code and not have them clash with the library's
own functions.

- The stdio destructor no longer resets the __iob pointer to NULL. This
avoids trouble with destructor functions which use stdio code. Unsolved
problem: the order in which destructors and constructors are called.

- Moved a few __delete_semaphore() calls into conditional compilation
sections where they should have been in the first place.

- Moved the data declarations out of math_data.c, stat_data.c,
socket_data.c, dirent_data.c and stdio_data.c and into the
code that initializes them.

- Moved the CPU/FPU type tests into the respective linker
libraries.