* defs.h (struct continuation_arg): make 'data' a union, to avoid
casting problems when int and pointer are not the same size.
* event-top.c (command_handler): use data as a union.
(command_line_handler_continuation): ditto.
* infcmd.c (step_1_continuation): use data as a union. Re-indent.
(step_once): ditto. (finish_command_continuation): ditto.
(finish_command): ditto.
* breakpoint.c (until_break_command): use data as a union.
(until_break_command_continuation): ditto.
* utils.c (add_intermediate_continuation): fix typo in comment.
* defs.h (struct continuation_arg): Change type of field 'data'
from PTR to void *.
* event-loop.h: Eliminate uses of PTR, use 'void *' instead.
* event-top.c: Ditto.