Remove prebuild ccan/opt dependencies

these must be rebuilt from source to match target headers
Silence warning if MAX/MIN is already defined
'llround' is more suitable here than 'roundl'
Fixup jansson & libusb include paths when using separate build directory
Improve performance of work generation by optimizing hex2bin and bin2hex

sprintf is a very expensive function, do direct translation instead.
KnC driver: knc-spi-fpga ASIC driver

This driver talks to KnCMiner controller via SPI

Protocol specification is available at
https://github.com/KnCMiner/jupiter-hw-docs/blob/master/fpga_spi.md
Better HW error count; disable permanently those cores which fail often