merge revision(s) r46331: [Backport #9885]

	* lib/net/imap.rb (body_type_1part): Gmail IMAP reports a body
	  type as "MIXED" followed immediately by params
	  [ruby-core:62864] [Bug #9885]
	  Patch by @rayners (David Raynes). [Fixes GH-622] 
	  https://github.com/ruby/ruby/pull/622


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@46617 b2dd03c8-39d4-4d8f-98ff-823fe69b080e