csplit cleanup.

csplit cleanup.

Be more careful about int widths.  For example, remove some
arbitrary limits by replacing 'unsigned' with 'size_t',
'uintmax_t', etc.  Use standard bool rather than a homegrown type.

(FALSE, TRUE, boolean): Remove.  All uses changed
to <stdbool.h> usage.
(struct control): offset is now intmax_t, not int.
repeat_forever is now bool, not int.
(struct cstring): len is now size_t, not unsigned int.
(struct buffer_record): bytes_alloc, bytes_used, num_lines are now
size_t, not unsigned.  start_line, first_available are now
uintmax_t, not unsigned.
(hold_count, control_used): Now size_t, not unsigned.
(last_line_number, current_line, bytes_written):
Now uintmax_t, not unsigned.
(save_to_hold_area, red_input, keep_new_line, record_line_starts,
create_new_buffer, get_new_buffer, load_buffer, find_line,
process_regexp, split_file, new_control_record, extract_regexp,
get_format_width, get_format_prec, max_out):
size args, locals, and returned values are now size_t, not unsigned
or int.
(get_first_line_in_buffer, find_line, write_to_file,
handle_line_error, process_line_count, regexp_error, process_regexp,
split_file):
File line, byte, and repetition counts are now uintmax_t, not unsigned.
(check_for_offset): Don't require a sign before the offset.
Use xstrtoimax to do the real work.
(extract_regexp): Remove harmful cast of size to unsigned.
256 -> 1<<CHAR_BIT, for clarity.
(get_format_flags): Return at most 3, to avoid worries about overflow.

(bytes_to_octal_digits): Remove.

(cleanup): Don't check whether output_stream is NULL, since
close_output_file does that for us.

(new_line_control, create_new_buffer): Use "foo *p = xmalloc
(sizeof *p);" instead of the more long-winded alternatives.

(get_new_buffer): Use O(1) algorithm for resizing a buffer
to a much larger size, instead of an O(N) algorithm.

(process_regexp): Use plain NULL rather than casted 0.

(make_filename): Use %u, not %d, to format unsigned file number.

(new_control_record): Use xrealloc exclusively, since it handles
NULL reliably,

(extract_regexp): Change misspelled word in diagnostic.

(get_format_width): Even if a minimum field width is specified,
allow room for enough octal digits to represent the value of
the maximum representible integer.  This fixes a potential
buffer overrun.  Calculate this room at compile-time, not
at run-time; this removes the need for bytes_to_octal_digits.
Check for overflow; this removes a FIXME.

(get_format_prec): Don't allow precision to be signed; it's
not ANSI.  Check for overflow.  Remove hardcoded "11" as
default precision; this fixes a potential buffer overrun
on hosts with wider size_t.

(get_format_conv_type): Change local variable to be of type
unsigned char, not int; this removes a potential subscript
violation on hosts where char is signed.

(max_out): Replace "for (;*p;)" with more-standard "while (*p)".
Allow "%%" in format.  Don't overflow when
counting lots of percents.

(usage): Default sprintf format is %02u, not %d.