Merge pull request #393 from kanoi/main

api -> drv
API V1.25 - add 'Last Valid Work' time for each device
API - return Last Valid Work
miner.php report 'Last Valid Work' as time before request
Implement and use usb_cleanup() on shutdown or restart
usb_cleanup() use correct locking mechanism
curses - fix - put a dev_width inside #ifdef
Hotplug - allow setting interval via --hotplug or API
api.c fix MSG overlap
README --hotplug
Release MMQ device only once (not 4 times)
make rw locks: mining_thr_lock and devices_lock
Merge pull request #381 from denis2342/hw_errors

several changes to avoid the display of hw errors
Merge pull request #394 from kanoi/main

Last Valid Work + usb_cleanup() + dev_width fix + --hotplug/API
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'