This function is a Luna alternative to fork() and exec().
Why? Simply because I can't figure out for the life of me how to implement a working fork().
So meanwhile, we have spawn() as a replacement. exec() still exists, though.
That's why we now have a VFS and a /dev pseudo-filesystem. To provide that kind of things.
Remember, everything is a file!!
The new way to ask the kernel for random numbers is to read from /dev/random.
Very bare-bones for now. Doesn't support arguments or environment (we don't have that stuff right now), and the executable is not a valid ELF, it terminates the task.
But it's a start!
Kernel: Implement a descriptor struct which stores the opened node and read offset, and give each task 8 of those.
Implement three syscalls: sys_read, sys_open and sys_close (sys_write still writes to the console instead of using a fd, for now)
Implement three new errors: ENOENT, EBADF and EMFILE.
libc: Implement the new errors, and the new syscalls in syscall().
Also fix _RETURN_WITH_ERRNO() to set errno correctly, which was making strerror() return null, thus crashing perror().
userspace: make init demonstrate the new file API.
The exit() libc function already accepted an integer, but didn't pass it on to the kernel since we had no mechanism for it to do that.
Now, the kernel stores a task's exit status to display it later (and in the future, return it to userspace via wait()/waitpid())
