player: Add macros to access basic player_sett_t flags.

Add macros PLAYER_IS_ACTIVE(), PLAYER_IS_AI() and PLAYER_HAS_MESSAGE().
Add knight management related macros PLAYER_SEND_STRONGEST(), PLAYER_CYCLING_KNIGHTS(), PLAYER_REDUCED_KNIGHT_LEVEL(), PLAYER_CYCLING_SECOND().
player: Add macros to access building permissions and spawn permission.

Add macros PLAYER_ALLOW_FLAG(), PLAYER_ALLOW_MILITARY() and PLAYER_CAN_SPAWN().
Move castle construction to game_build_castle().
player: Fix name of road_valid_dir field.
player: Add function player_build_road().

Constructs a road non-interactively from an initial position and a list of directions.
game: In game_prepare_ground_analysis() do not rely on player structure.

Instead return result in a plain array.