Potentially more optimisable constants.
Properly prepare .data and .bss sections.
More consistency in #if vs. #ifdef usage.
For now initialize programmer's address from EEPROM.

Temporarily read the address to send the ACK packets to from the EEPROM.
What we really need to do though is initally disable ACKing until we
receive a proper 3-byte packet from the programmer, contianing its
address.  Then we can re-enable ACKs.
For now delay every Tx by 1ms to allow remote end to switch to Rx.