Options -r and -o should be combinable

This module should explain it:

# When using the 'r' and 'o' option together, you should be able to combine the
# flags into one command to generate ri documentation for a given output
# destination. Such as:
#
# rdoc -ro mydocs lib/mylib.rb
#
module MyLib
  def yaknow
    puts "oh, totally"
  end
end

When you try: rdoc -ro mydocs lib/mylib.rb what you actually see is:

invalid options: -ro
(invalid options are ignored)

Reproduce the behavior with rdoc -ro mydocs lib/mylib.rb and compare it with the separate -r and -o options. Trace the rdoc command-line option parsing and make the combined flags accepted while preserving the requested ri documentation destination; done when the example command succeeds without the invalid-options warning.