Change default avalon target temperature to 50 degrees.
Update README with avalon temp default.
Add an --avalon-cutoff feature which puts the avalon idle should it reach this temperature, defaulting to 60, re-enabling it when it gets to target temperature.
Add an avalon-auto option which enables dynamic overclocking based on hardware error rate for maximum effective hashrate.
Update NEWS.
Bump version number to 3.3.1
Reset the other auto counters in avalon when idling a device.
Move to slightly more relaxed timeouts for avalon.
Support all avalon frequencies on the command line.
Merge pull request #456 from kanoi/master

cps and usbdev locking