initialize the mcu from avr_init.S, implemented timeout function, enabling the application after a while.

clr r25 in rfm12_trans, from rfm12_wait_read don't call rfm12_trans but jump it and let it call ret for us.

get rid of any stdlib code, declare main as naked and do avr initialization (stack, etc.) on our own.

funkloader.c: configure SPI_DDR using two calls, which are translated to sbi instructions (instead of read/or/write).

rfm12_trans.S, rfm12_wait_read.s: define __SFR_OFFSET to zero, so we don't have to subtract 0x20 here and there.