Use SDRAM on the Papilio Pro

Based on code by Robert Jordens
bios: remove references to 'DDR' SDRAM, as we also support SDR SDRAM
bios/crt0.S: remove unused macaddr, add syscall handler stub
spiflash: redundant slice
crt: add umoddi3
programmer: make xc3sprog verbose
bios: shorten abort wait and move flashboot last
memtest: papilio pro sdram changes