arch-atmega/uart.c: save flash space by not using atol anymore

Signed-off-by: Aurelio Colosimo <aurelio@aureliocolosimo.it>
arch-atmega: save ram (bss) space by allocating uart buffer at runtime

Signed-off-by: Aurelio Colosimo <aurelio@aureliocolosimo.it>
mcuio: "mcuio alive" task made optional (and not set by default)

Signed-off-by: Aurelio Colosimo <aurelio@aureliocolosimo.it>
arch-atmega/usb-uart.c: fix usb ids

Signed-off-by: Aurelio Colosimo <aurelio@aureliocolosimo.it>