A1: happy new year 2014
A1: replace malloc failure checks with asserts
A1: adjust debug verbosity levels
A1: remove sleeps in SPI poll cycles

RasPi seems to have a timer granularity of 40ms, which makes
usleep() calls with lower values unusable. Remove them between
polling SPI accesses.
A1: remove dead code
A1: ensure both job items are queued at scanwork()
A1: (debug/testing) temporary deactivate chips on comm errors
A1: consider number of chips in chain for SPI polling
A1: add --enable-bitmine_A1 options
A1: add PLL configuration functionality
A1: (debug/testing) add manual chip enumeration