kernel: scheduler: implement end_task
boot: sam7s: fix save user mode context, move ack int
mach-at91: pit: create pit_read_pivr function
kernel: scheduler: call pit_read_pivr to ack it
mach-at91: sam7s: implement default_spurious_handler
mach-at91: sam7s: enable aic debug
boot: sam7s: clear interrupt, change temp register
include: task: change stack start offset
mach-at91: pio: implement pio-core driver and pio arch functions
mach-at91: pio: disable some pio function
kernel: main: trying to playing with leds in tasks