port gnugo to javascript with emscripten

build_gnugo.sh is used to generate necessary step database

rebuild_gnugo_with_em.sh is used to generate gnugo.js

gnugowrapper.c is the main source file for gnugo.js to export APIs from GNU-Go (much code copied from play_ascii.c from gnugo source)

To compile gnugo correctly:

• disable clock functionality: make gg_gettimeofday return 0 directly

Currently we support APIs:

• Module._initializeGoGame(boardSize, komi, handicap, randomSeed)
• Module._finalizeGoGame()
• Module._getBoard(i, j)
• Module._isLastMove(i, j)
• Module._genNextStep(): make computer put current stone at a proper place
• Module._moveTo(i, j): put current stone at (i,j), where 0 < i,j < size

after compiled out gnugo.js, try test.html with it. if want to interact with the board, open browser console panel, and try Module._moveTo(0, 0); showBoard(syncBoard(board)) to put one stone at A1.