libctf: eschew %zi format specifier

Too many platforms don't support it, and we can always safely use %lu or
%li anyway, because the only uses are in debugging output.

libctf/
	* ctf-archive.c (ctf_arc_write): Eschew %zi format specifier.
	(ctf_arc_open_by_offset): Likewise.
	* ctf-create.c (ctf_add_type): Likewise.