2020 fixes

[lemonsqueeze]

Good thing with lockdown, I have some time to take care of Pachi =)

Mostly fixes a few bugs in previous PRs, and makes windows build almost 3x faster.

• Fixed DOUBLE_FLOATING issue
• Distributed engine works again, forgot to convert it in gtp_setoption PR (#111)
• Fixed undo timer issue. With things like 'pachi -t 10', Pachi would stop thinking if you undo + genmove immediately in gogui / sabaki etc.
• UCT: Lowered uct pass_limit, helps with early pass for short games (esp. japanese rules)
• KGS: --nopassfirst only applies to chinese rules games
• Fixed board_earliest_pass() bug, values were wrong !
• --fuseki-time stops after move 10 instead of 20, helps with trick plays