Prefer defvar-local in play/*.el

Prefer defvar-local in play/*.el

* lisp/play/5x5.el
(5x5-grid, 5x5-x-pos, 5x5-y-pos, 5x5-moves, 5x5-cracking):
* lisp/play/decipher.el (decipher-alphabet)
(decipher-stats-buffer, decipher-undo-list-size)
(decipher-undo-list):
* lisp/play/gamegrid.el (gamegrid-use-glyphs)
(gamegrid-use-color, gamegrid-font, gamegrid-face)
(gamegrid-display-options, gamegrid-buffer-width)
(gamegrid-buffer-height, gamegrid-blank, gamegrid-timer)
(gamegrid-display-mode, gamegrid-display-table)
(gamegrid-face-table, gamegrid-buffer-start)
(gamegrid-score-file-length):
* lisp/play/snake.el (snake-length, snake-velocity-x)
(snake-velocity-y, snake-positions, snake-score, snake-paused)
(snake-moved-p, snake-velocity-queue):
* lisp/play/tetris.el (tetris-shape, tetris-rot)
(tetris-next-shape, tetris-n-shapes, tetris-n-rows)
(tetris-score, tetris-pos-x, tetris-pos-y, tetris-paused):
Prefer defvar-local.

* lisp/play/5x5.el (5x5-defvar-local): Make obsolete.