Add tests for compound matching on Output matchers

This is the issue reported in #1391 - expecting like

    expect { puts "foobar" }
      .to output.to_stdout(/foo/)
      .and output.to_stdout(/bar/)

fails, because the two matchers get nested, and inner matcher catches
the stream write, hiding it from the outer one.

spec/rspec/matchers/built_in/output_spec.rb

@@ -139,6 +139,12 @@ def invalid_block
       }.to fail_including("expected block to not output a string starting with \"f\" to #{stream_name}, but output \"foo\"\nDiff")
     end
   end
+
+  context "expect { ... }.to output(matcher1).#{matcher_method}.and output(matcher2).#{matcher_method}" do
+    it "passes if the block outputs lines to #{stream_name} matching both matchers" do
+      expect { print_to_stream "foo_bar" }.to matcher(/foo/).and matcher(/bar/)
+    end
+  end
 end
 
 module RSpec