Customizable UCI output mechanism

Instead of writing it to cout, collect whole output in string stream and
emit it with overridable handler.
Disable some platform-specific behaviours

Depending on target platform or compiler, several optimizations
(including raw assembly language) could be inserted.  Disable them.
fu makefile
Print debug output to proper stream

Sync_cout no longer uses std::cout so that needed to be updated.
Problematic line removed from benchmark

Synchronous wait removed instead of reworking it.  Benchmark may be
broken now.
fu makefile
Demo: In-browser game player vs Stockfish