OPT_PARSE_LIST_OBJECTS_FILTER_INIT() with a non-NULL second argument
passes a function pointer via an object pointer, which is undefined. It
may work fine on platforms that implement C99 extension J.5.7 (Function
pointer casts). Remove the unused macro and avoid the dependency on
that extension.
Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>