clib2 Code

- 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.

- Cleaned up the 68k build makefile, so that the CPU and FPU
tests and the error message display can run safely even
on plain 68000 machines. This won't work for the 32 bit small
data model, which implies 68020 code, but so there...

- Made the file descriptor checks in the fsync() and fdatasync()
functions more robust.