intel64: pass a IRQ number to notify_interrupt()
set "io" as BUILTIN_SERVERS
userland: implement io_*
hal_atomic_cas64() now returns bool whether "replacement" was written
userland: implement hal_atomic_cas64()
tiny fix for some header files
rename "hal_enable_irq()" to "enable_irq()"
userland: implement enable_irq()
replace strncpy() with strlcpy()