maint.mk: s/_header_without_use/_sc_header_without_use/

maint.mk: s/_header_without_use/_sc_header_without_use/

* top/maint.mk (_sc_header_without_use): Rename from _header_without_use.
(sc_prohibit_assert_without_use): Use the new name.
(sc_prohibit_close_stream_without_use): Likewise.
(sc_prohibit_getopt_without_use): Likewise.
(sc_prohibit_quotearg_without_use): Likewise.
(sc_prohibit_quote_without_use): Likewise.
(sc_prohibit_long_options_without_use): Likewise.
(sc_prohibit_inttostr_without_use): Likewise.
(sc_prohibit_ignore_value_without_use): Likewise.
(sc_prohibit_error_without_use): Likewise.
(sc_prohibit_xalloc_without_use): Likewise.
(sc_prohibit_hash_without_use): Likewise.
(sc_prohibit_hash_pjw_without_use): Likewise.
(sc_prohibit_safe_read_without_use): Likewise.
(sc_prohibit_argmatch_without_use): Likewise.
(sc_prohibit_canonicalize_without_use): Likewise.
(sc_prohibit_root_dev_ino_without_use): Likewise.
(sc_prohibit_openat_without_use): Likewise.
(sc_prohibit_c_ctype_without_use): Likewise.
(sc_prohibit_signal_without_use): Likewise.
(sc_prohibit_intprops_without_use): Likewise.