diff-parseopt: correct variable types that are used by parseopt

Most number-related OPT_ macros store the value in an 'int' variable. Many of the variables in 'struct diff_options' have a different type, but during the conversion to using parse_options() I failed to notice and correct. The problem was reported on s360x which is a big-endian architechture. The variable to store '-w' option in this case is xdl_opts, 'long' type, 8 bytes. But since parse_options() assumes 'int' (4 bytes), it will store bits in the wrong part of xdl_opts. The problem was found on little-endian platforms because parse_options() will accidentally store at the right part of xdl_opts. There aren't much to say about the type change (except that 'int' for xdl_opts should still be big enough, since Windows' long is the same size as 'int' and nobody has complained so far). Some safety checks may be implemented in the future to prevent class of bugs. Reported-by: Todd Zullinger <tmz@pobox.com> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>