Added preliminary support for execve(). Updates to clone, fork, exit, task handling.

It turned out we used one version of kmalloc for malloc() and another for kfree()!
Now fixed.
Added parent-child relationship to tasks. Need to polish handling CLONE_PARENT and THREAD.

src/api/thread.c

@@ -76,6 +76,10 @@ int thread_destroy(struct task_ids *ids)
 	 */
 	BUG_ON(task->wqh_pager.sleepers > 0);
 
+	/*
+	 * FIXME: We need to free the pgd and any thread specific pmds!!!
+	 */
+
 	/* We can now safely delete the task */
 	free_page(task);