Retire ScalePawnSpan[]

Obscure, undocmented and misnamed array. Replace with
the direct formula: it is much more clear what the
code does.

No functional change.

Resolves #90
Restore std::dec after std::hex

Code is leaking a std::hex, and causes subsequent
sync_cout output to be in hexadecimal.

Spotted by Lucas

No functional change.
Merge branch 'official' into min_split_depth
Decrease minimumSplitDepth to 6

When we have more than 14 threads running.

bench: 6564212