Merge pull request #653 from Canaan-Creative/temp

Reset ipv6 flag to false in every api-allow loop
Increase max diff on sp30 to 1024
Hashfast voltage support
Set hashfast voltage settings only when really needed
Send hfa generic frame only if voltage was specified on the command line for that device
Drivers that take a diff should specify a max diff or it is assumed they don't support one so set max_diff to 1 if unset
Set CLOEXEC on sockets on linux
Suspend stratum on removing a pool
Set the correct flag for close on exec for sockets
Save pools in priority order at time of writing config
Fix segfault when writing config with hashratio built in
Implement support for pool ping and json integers of zero in getversion and ping
Filter responses that don't have a result
stratum_rthread sleep only 3s when all the pool have disconnected

Signed-off-by: Yi Zhang <tyouicn@gmail.com>
Merge pull request #655 from joycn/master

stratum_rthread sleep only 3s when all the pool have disconnected
Merge branch 'master' of github.com:ckolivas/cgminer
Add warning against system libusb in configure help
Make it impossible to configure in more than one device that is meant to be standalone. Add more information to configure help, along with comments for new drivers.
Selectively yield on dropping a lock only on single CPU platforms
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