Clear last pool work on switching pools if the current pool supports local work generation or we are in failover only mode.
configure - set USE_USBUTILS when usbutils is required and use it in the code
Merge pull request #395 from kanoi/bflsc

configure - set USE_USBUTILS when usbutils is required and use it in the code
usbutils.c copy full size to 'Last Command'
Instead of keeping track of when the last work item was generated to keep stratum connections open, keep them open if any shares have been submitted awaiting a response.
Merge pull request #397 from kanoi/bflsc

usbutils.c copy full size to 'Last Command'
Make sure to retry only once with noresume support for stratum.