pthread malloc

Hi!  I added pthread support for alloc.
Now all [__libc_]{malloc|realloc|calloc|free}
are thread safe.  Actually I modified only malloc and free.
This make them with 20-30 bytes bigger.

My thread safe implementation is shorter than current
dietlibc (not thread save).  It was difficult to test
if all works good.  I wrote the program tst-pthread
to check all.  Its work fine for me.  It's nice if someone
reproduce my test on other ARCH.

Shortly:
	make
	make tests
	./tst-pthread   # for each operation prints one letter
See what happen in memory in "mmap_file"

I used only this for locking/unlocking:
   #define alloc_LOCK()		pthread_mutex_lock(&__alloc_mutex_lock)
   #define alloc_UNLOCK()	pthread_mutex_unlock(&__alloc_mutex_lock)

and in the source using this macro.  I see in dietlibc
dietlibc/libpthread/pthread_sys_alloc.c
one uses:

  __NO_ASYNC_CANCEL_BEGIN_(this);

I'm not threads expert.  I'm not shure, that my locks
are safe (if theyavoids deadlock).  Please chek it and
say if some problems arises.

Nikola

http://riemann.fmi.uni-sofia.bg/programs/diet/alloc.tar.gz