libroot: Remove some old TODOs from fork() implementation.

The first was added in 2004 when there wasn't even a branch for
initializing the child; I think this can be considered done now.
The second was added in 2010, but it seems in the meantime we've
decided that reinitializing locks is the best way to make them
consistent after calling fork(), so it's also obsolete.

src/system/libroot/posix/unistd/fork.c

@@ -154,14 +154,10 @@ fork(void)
 	thread = _kern_fork();
 	if (thread == 0) {
 		// we are the child
-		// ToDo: initialize child
 		__main_thread_id = find_thread(NULL);
 		pthread_self()->id = __main_thread_id;
 
 		mutex_init(&sForkLock, FORK_LOCK_NAME);
-			// TODO: The lock is already initialized and we in the fork()ing
-			// process we should make sure that it is in a consistent state when
-			// calling the kernel.
 		__gRuntimeLoader->reinit_after_fork();
 		__heap_after_fork_child();
 		__reinit_pwd_backend_after_fork();