[kaffe] Shutdown & new syscalls

[Guilhem Lavaux]

Hi everyone,

I have just committed two small sets of patches:
* the first one is to fix a misbehaviour in the shutdown sequence, the 
previous one was causing an assertion failed in jthread_exit in some 
cases when two threads exit at the same time.
* the second is a prepatch for the NIO stuff. We will need the syscalls 
mmap, munmap and ftruncate so I added them in jsyscalls.h and propagated 
the implementation in kaffe/kaffevm/systems (at least for the system I 
know) the others are just dummy. I always hope Michael answer me about 
its NIO implementation...

Cheers,

Guilhem.