range-diff: use parse_options() instead of diff_opt_parse()

range-diff: use parse_options() instead of diff_opt_parse()

Diff's internal option parsing is now done with 'struct option', which
makes it possible to combine all diff options to range-diff and parse
everything all at once. Parsing code becomes simpler, and we get a
looong 'git range-diff -h'

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>