* keyboard.c: Integer and memory overflow fixes.

* keyboard.c: Integer and memory overflow fixes.

(read_char, menu_bar_items, tool_bar_items, read_char_x_menu_prompt)
(read_char_minibuf_menu_width, read_char_minibuf_menu_prompt)
(follow_key, read_key_sequence): Use ptrdiff_t, not int, to count maps.
(read_char_minibuf_menu_prompt): Check for overflow in size
calculations.  Don't update size until allocation succeeds.  Redo
calculations to avoid overflow.
* keyboard.h: Change prototypes to match the above.