Update porting guide
WM8904: Don't use MSEC2TICK in timeout calculation
Minor documentation update
Move POSIX message queue files from sched/ to sched/mqueue
Move signal-related files from sched/ to sched/signal
Move all pthread files from sched/ to sched/pthread
Move environment files from sched/ to sched/environ
Update ChangeLog
Move group logic from sched/ to sched/group
Move watchdog functions from sched/ to sched/wdog
Move interrupt dispatch logic from sched/ to sched/irq
Move clock functions from sched/ to sched/clock
Move POSIX timer files from sched/ to sched/timer/
Update ChangeLog
Move page fill sources from sched/ to sched/paging
Move initialization functions from sched/ to sched/init
Move errno related files from sched/ to sched/errno
Move task control files from sched/ to sched/task
Move a few files in sched/ that did not seem to have a home to sched/signal and sched/task
Partial (non-working) checked in before the big, risky automated change