merge revision(s) 43954: [Backport #9125]

	* lib/net/smtp.rb (Net::SMTP#critical):  Always return a
	  Net::SMTP::Response.  Patch by Pawel Veselov.
	  [ruby-trunk - Bug #9125]

	* test/net/smtp/test_smtp.rb:  Test for the above.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@44393 b2dd03c8-39d4-4d8f-98ff-823fe69b080e