Simulation: Change how simulated UART data availability is signaled.  The last change is not safe (but I don't like this workaround either -- maybe something better will come to me).

simulation: Add a simulatied UART input device.  Also lots of misc clean-up for stylistic compatibility with other architectures

Repartition some message queue logic: sched/mqueue should have all mqueue knowledge; fs/mqueue should deal only with inodes

Fix some unbalanced sched_lock()/sched_unlock() pairs int the re-implemented VFS semaphore and message queue logic

Convert mqueue structure for use in VFS as inode data; rename mqueue_inode_s; remove links, reference counts and name from mqueue structure.  These will be replaced by VFS data.  Remove g_msgqueues and mq_findnamed.c; these will be replace with VFS logic

Fix some comments:  Remove button description from GPIO interrupt handlers that derive from the button interrupt handler

More vfork():  If we get to vfork() via system call, then we need to clone some system call information so that the return form the cloned system call works correctly