A start on clearing up -Wunused-parameter warnings.

about halfway done, as it stands here.

The three main types of warning-suppressing changes (other than actual fixes and removing parameters) are (using example `nullfunction(game *g, int x, int y) {}`):
* remove the parameter names `nullfunction(game *, int, int) {}`
* explicitly cast to void `nullfunction(game *g, int x, int y) { (void)g; (void)x; (void)y; }`
* comment out the parameter name `nullfunction(game * /*g*/, int /*x*/, int /*y*/) {}`
used according to situation.