This patch undoes the change in the order of timer parameters for:
net.accept() net.recv() tmr.delay() tmr.setclock() tmr.set_match_int()
tmr.gettimediff() and also changes the new tmr.getdiffnow() to have the
same parameter ordering as the others.
The default timer ID (the systimer), which previously was obtained with an
optional last parameter, is now obtained by supplying nil as the timer ID.
Generic info/eLua interrupt handlers: using interrupt handlers from Lua and C
Platform interface/CPU: updated CPU platform interface
Platform interface/Timers: updated timers platform interface
Generic modules/cpu: updated CPU module documentation
Generic modules/tmr: updated timer module documentation
eLua internals/Overview/Implementing interrupts: interrupt handlers implementation guide
Also minor bugfixes in the interrupt implementation.
