Add set union to Options

Library/Homebrew/options.rb

@@ -83,6 +83,10 @@ class Options
     Options.new(@options & o)
   end
 
+  def |(o)
+    Options.new(@options | o)
+  end
+
   def *(arg)
     @options.to_a * arg
   end

Library/Homebrew/test/test_options.rb

@@ -126,6 +126,13 @@ class OptionsTests < Test::Unit::TestCase
     assert_equal [foo], (@options & options).to_a
   end
 
+  def test_set_union
+    foo, bar, baz = %w{foo bar baz}.map { |o| Option.new(o) }
+    options = Options.new << foo << bar
+    @options << foo << baz
+    assert_equal [foo, bar, baz].sort, (@options | options).to_a.sort
+  end
+
   def test_coerce_with_options
     assert_same @options, Options.coerce(@options)
   end