tr cleanup, mostly having to do with integer type ranges.

tr cleanup, mostly having to do with integer type ranges.
Remove all casts.

Here are examples of the failures:

   $ echo a | tr a '[x*][y*2147483646][y*2147483646][y*4]'
   x
   $ echo abcd | tr abc '[b*\9]'
   bbbd
   $ echo abcd | tr abc '[b*0]'
   tr: invalid repeat count `0' in [c*n] construct
   $ echo abcd | tr -c '[a*65536]\n' '[b*]'
   tr: ../../coreutils-5.2.1/src/tr.c:1942: main: Assertion `get_next (s2, ((void *)0)) == -1 || truncate_set1' failed.
   Aborted

(N_CHARS, N_CHAR_CLASSES): Now an enum, not a macro.
This is safe since the code already assumes N_CHARS fits in int.
(Filter): Remove: we want to prototype everything.
(ORD, CHR): Remove.  All uses removed.  Some replaced with:
(uchar): New function.  All places where a char must be converted
to an unsigned char are now done this way, not by ad-hoc methods.
(count): New type.  Use it whenever counts or states are needed.
(BEGIN_STATE): Increase from INT_MAX - 1 (which was bogus, anyway,
since we used it in an unsigned int context) to UINTMAX_MAX - 1.
(REPEAT_COUNT_MAXIMUM): New macro.  Use it in place of BEGIN_STATE
whenever appropriate.
(NOT_A_CHAR): Remove global macro; now a local enum.
(UL_LOWER, UL_UPPER, UL_NONE): No longer specify values, since
the rest of the code no longer depends on them.
(class_ok): Remove; all uses changed to use inline comparisons.
(RE_NO_TYPE): Remove; wasn't used or needed.
(struct List_element): normal_char and equiv_code are now unsigned
char, not int.
first_char, last_char, and the_repeated_char are now unsigned char,
not unsigned int.  repeat_count is now count, not size_t.
All uses changed.
(struct Spec_list): state is now count, not unsigned int.
lengthis now count, not size_t.
n_indefinite_repeats is now size_t, not int.
has_equiv_class, has_char_class, and has_restricted_char_class
are now bool, not int.  All uses changed.
(struct E_string): s is now char *, not unsigned char *.
escaped is now bool *, not int *.  All uses changed.
(ES_MATCH): Remove macro, replacing with:
(es_match): New inline function.  All uses changed.
(squeeze_repeats, complement, posix_pedantic, truncate_set1,
translating): Now bool, not int.
(io_buf): Now char array, not unsigned char.
(SET_TYPE): Remove.  All uses replaced with bool.
(is_equiv_class_member, unquote, append_range, append_char_class,
append_equiv_class, find_closing_delim, star_digits_closebracket,
build_spec_list, parse_str, homogeneous_spec_list):
Now returns bool, not int.  All uses changed.
(is_equiv_class_member): Now inline.
(is_equiv_class_member, is_char_class_member, make_printable_str,
append_normal_char, append_range, append_repeated_char,
get_s2_spec_stats):
Args are now of proper integer type.
(unquote, look_up_char_class, make_printable_str,
append_equiv_class, build_spec_list, squeeze_filter):
Avoid unsigned char *p; gently convert *p to unsigned char instead.
(unquote, get_spec_stats): Do not jump past declarations and then
use them; C doesn't allow this in portable programs.
(make_printable_str): Check for overflow in size calculations.
(xmemdup): Remove.  All uses rewritten.
(find_bracketed_repeat): Args are now of proper pointer-to-integer
type.  Do not reject [c*0].  Use xstrtoumax, not xstrtoul.
(find_bracketed_repeat, star_digits_closebracket): Check that the
digits are not escaped.
(build_spec_list): Don't bother to copy opnd_str; not needed.
(build_spec_list, get_next): Simplify internal logic a bit.
(card_of_complement): Fix bug due to char overflow.
(get_spec_stats): Don't assume len fits into int.
Check for integer overflow.  Use abort() rather than assert(0).
(string2_extend): Fix subscript error: is_char_class_member (..., 255)
was being invoked.
(squeeze_filter): READER is never null now; simplify code.
READER arg now has a simpler type.  Remove unnecessary casts.
(squeeze_filter, main): Calls to fwrite improperly checked result
against zero, rather than against requested size.
(plain_read): New function.
(read_and_delete, read_and_xlate):
Remove unused filter arg, and don't worry about hit_eof.
Simplify by using plain_read.
(set_initialize): Args are bool and bool *, not int and SET_TYPE *.
(main): Always pass a non-null procedure to squeeze_filter.
Rewrite so that class_ok isn't needed.