Changeset 461 for soft/giet_vm/giet_libs/user_lock.h

1) replace the "giet_locks.c" library by the "user_lock.c" library (the new library uses a ticket allocator).
2) introduce new syscalls in the stdio.c file, to support the NIC peripheral.
3) modify the MWMR library to use the lock with ticket allocator, and to separate the fifo descriptor and the data buffer.