More wordsplit int cleanup

More wordsplit int cleanup

* lib/wordsplit.c: Include limits.h.
(_wsplt_subsplit, wordsplit_add_segm, wsnode_quoteremoval)
(wsnode_coalesce, wsnode_tail_coalesce, find_closing_paren)
(expvar, begin_var_p, node_expand, begin_cmd_p, expcmd)
(scan_qstring, scan_word, wordsplit_c_quoted_length)
(wordsplit_string_unquote_copy, wordsplit_c_quote_copy)
(exptab_matches, wordsplit_process_list):
Prefer bool to int.
(wordsplit_init, alloc_space, coalesce_segment)
(wsnode_quoteremoval, wordsplit_finish, wordsplit_append):
Use WRDSE_OK instead of 0 when the context is that of WRDSE_*.
(wsnode_flagstr, coalesce_segment, wsnode_quoteremoval)
(wordsplit_finish, node_split_prefix, wsplt_assign_var, expvar)
(expcmd, wordsplit_tildexpand, wordsplit_pathexpand)
(wsplt_unquote_char, wsplt_quote_char)
(wordsplit_string_unquote_copy):
Prefer '\0' to 0 when it is a char.
(wsnode_insert): Omit last arg, which was always 0.
All callers changed.
(wordsplit_add_segm, node_split_prefix):
Use unsigned, not int, for flag, for consistency.
(wordsplit_finish, begin_var_p, begin_cmd_p, skip_sed_expr)
(xtonum, wsplt_unquote_char, wsplt_quote_char)
(wordsplit_c_unquote_char, wordsplit_c_quote_char)
(wordsplit_c_quote_copy):
Prefer char to int for chars.
(xtonum): Don’t treat "\400" as if it were "\000".