Some warnings are because the @o.rb_scan_args call doesn't
include keyword arguments, but the first argument is passed to
rb_scan_args may have a last hash treated as keywords.  Those
should be handled using rb_scan_args_kw on Ruby 2.7.

Other warnings are for the deprecated rb_scan_args behavior to
split option hashes or treat a nil argument as an option hash.
Those warnings should just be suppressed.