Clean up so we can compile with g++
Switch to .cc extensions
Continue removal of global variable usage.

(And move unused files out of src directory).
Add Board class
Add IsGameOver function to the board.
Add a IsGameOverExpensive method to the board.
Move positional values into a nice little class.
Major clean up of the hashtable/transposition table code.

Working towards a nice class that will clean up all the global
variables.