Target for v1.5:
-- make X and raw two different display drivers
- integrate H.G.Muller's work on the xboard protocol on top of new driver-like
display handling
- deprecate xshogi in favor of xboard
- make it battle against Mutz-era gnushogi, and other engines, and
compare their evaluation results
- see what needs updating in book
+- express available commands as display-dependant, instead of using if(XSHOGI)
+ - make "help" list commands available for current display
+- make X and raw two different display drivers