(exit_status): Remove. Now done by passing a boolean

(exit_status): Remove.  Now done by passing a boolean
'ok' flag around.
(simple_cat, cat): Return true if successful.  All callers changed.
(simple_cat, cat, main): Use bool for booleans.
(simple_cat): Use size_t for sizes.
(cat, main): Use the same names for parameters that we use for
long options, to avoid confusion.  This inverts the sense of the
show_tabs (formerly output_tabs) and number_nonblank
(formerly numbers_at_empty_lines) variables.
(main): Don't mess up (due to integer overflow) if we are given
INT_MAX - INT_MIN + 1 options.
[O_BINARY]: Don't invoke isatty unless the other options require it.
(main): When deciding whether to use simple_cat, don't worry
about binary option; it's irrelevant.