Fix pic24 mib bug

This was a nasty one (the bus would normally lock when trying to send a report, rendering the device unmanageable until a power cycle) that I fixed mostly on a hunch.  The issue was that adding and removing items from the rpc_queue was interruptible, meaning an interrupt could come along and make garbage out of whatever we're trying to send.

Also added a bunch more logging and moved some files around.