Use a lowercase driver name to fix --scan pattern matching
Otherwise the following doesn't work: -S noauto -S twinfury:auto
Merge pull request #354 from nwoolls/bug/twinfury-scan-arg

Use a lowercase driver name to fix --scan pattern matching
x6500: Allow overriding the maximum frequency used by the dynclock logic
Can now use e.g. --set-device x6500:maxclock=210
Prevents spending time on frequencies that only produce HW errors
Merge branch 'bfgminer' of https://github.com/luke-jr/bfgminer into bfgminer