lib: fix type and comment Game::last_turn

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
lib: fix the fix of Float::abs

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
lib: make the getter of HashMapWithDefault::default_val public

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>