checkhash: some work on a faster variant (wip)

This should not be used for all algos... not enabled yet

todo: multiple nounces or blake32 style checkup
Rework benchmark mode and min/max range

Was maybe my fault, but the benchmark mode was
always recomputing from nonce 0.

Also fix blake if -d 1 is used (one thread but second gpu)

stats: do not use thread id as key, prefer gpu id...